Product ( mathematics ) - wikipedia Product ( mathematics ) This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( November 2014 ) Calculation results Addition ( + ) summand + summand addend ( broad sense ) + addend ( broad sense ) augend + addend ( strict sense ) ) = ( displaystyle scriptstyle left. ( \begin ( matrix ) scriptstyle ( \text ( summand ) ) , + , ( \text ( summand ) ) scriptstyle ( \text ( addend ( broad sense ) ) ) , + , ( \text ( addend ( broad sense ) ) ) scriptstyle ( \text ( augend ) ) , + , ( \text ( addend ( strict sense ) ) ) end ( matrix ) ) \right ) , = , ) sum ( displaystyle scriptstyle ( \text ( sum ) ) ) Subtraction ( − ) minuend − subtrahend = ( displaystyle scriptstyle ( \text ( minuend ) ) , - , ( \text ( subtrahend ) ) , = , ) difference ( displaystyle scriptstyle ( \text ( difference ) ) ) Multiplication ( × ) factor × factor multiplicand × multiplier ) = ( displaystyle scriptstyle left. ( \begin ( matrix ) scriptstyle ( \text ( factor ) ) , \times , ( \text ( factor ) ) scriptstyle ( \text ( multiplicand ) ) , \times , ( \text ( multiplier ) ) end ( matrix ) ) \right ) , = , ) product ( displaystyle scriptstyle ( \text ( product ) ) ) Division ( ÷ ) dividend divisor numerator denominator ) = ( displaystyle scriptstyle left. ( \begin ( matrix ) scriptstyle ( \frac ( scriptstyle ( \text ( dividend ) ) ) ( scriptstyle ( \text ( divisor ) ) ) ) scriptstyle ( \text ( ) ) scriptstyle ( \frac ( scriptstyle ( \text ( numerator ) ) ) ( scriptstyle ( \text ( denominator ) ) ) ) end ( matrix ) ) \right ) , = , ) fraction quotient ratio ( displaystyle ( \begin ( matrix ) scriptstyle ( \text ( fraction ) ) scriptstyle ( \text ( quotient ) ) scriptstyle ( \text ( ratio ) ) end ( matrix ) ) ) Modulo ( mod ) dividend mod divisor = ( displaystyle scriptstyle ( \text ( dividend ) ) ( \bmod ( \text ( divisor ) ) ) , = , ) remainder ( displaystyle scriptstyle ( \text ( remainder ) ) ) Exponentiation base exponent = ( displaystyle scriptstyle ( \text ( base ) ) ^ ( \text ( exponent ) ) , = , ) power ( displaystyle scriptstyle ( \text ( power ) ) ) nth root ( √ ) radicand degree = ( displaystyle scriptstyle ( sqrt ( ( \text ( degree ) ) ) ( scriptstyle ( \text ( radicand ) ) ) ) , = , ) root ( displaystyle scriptstyle ( \text ( root ) ) ) Logarithm ( log ) log base ⁡ ( antilogarithm ) = ( displaystyle scriptstyle log _ ( \text ( base ) ) ( ( \text ( antilogarithm ) ) ) , = , ) logarithm ( displaystyle scriptstyle ( \text ( logarithm ) ) ) In mathematics, a product is the result of multiplying, or an expression that identifies factors to be multiplied. Thus, for instance, 6 is the product of 2 and 3 ( the result of multiplication ), and x ⋅ ( 2 + x ) ( displaystyle x cdot ( 2 + x ) ) is the product of x ( displaystyle x ) and ( 2 + x ) ( displaystyle ( 2 + x ) ) ( indicating that the two factors should be multiplied together ). The order in which real or complex numbers are multiplied has no bearing on the product ; this is known as the commutative law of multiplication. When matrices or members of various other associative algebras are multiplied, the product usually depends on the order of the factors. Matrix multiplication, for example, and multiplication in other algebras is in general non-commutative. There are many different kinds of products in mathematics : besides being able to multiply just numbers, polynomials or matrices, one can also define products on many different algebraic structures. An overview of these different kinds of products is given here. Contents 1 Product of two numbers 1.1 Product of two natural numbers 1.2 Product of two integers 1.3 Product of two fractions 1.4 Product of two real numbers 1.5 Product of two complex numbers 1.5. 1 Geometric meaning of complex multiplication 1.6 Product of two quaternions 2 Product of sequences 3 Commutative rings 3.1 Residue classes of integers 3.2 Rings of functions 3.3 Convolution 3.4 Polynomial rings 4 Products in linear algebra 4.1 Scalar multiplication 4.2 Scalar product 4.3 Cross product in 3 - dimensional space 4.4 Composition of linear mappings 4.5 Product of two matrices 4.6 Composition of linear functions as matrix product 4.7 Tensor product of vector spaces 4.8 The class of all objects with a tensor product 4.9 Other products in linear algebra 5 Cartesian product 6 Empty product 7 Products over other algebraic structures 8 Products in category theory 9 Other products 10 See also 11 Notes 12 References 13 External links Product of two numbers Main article : multiplication Product of two natural numbers 3 by 4 is 12 Placing several stones into a rectangular pattern with r ( displaystyle r ) rows and s ( displaystyle s ) columns gives r ⋅ s = ∑ i = 1 s r = ∑ j = 1 r s ( displaystyle r cdot s = sum _ ( i = 1 ) ^ ( s ) r = sum _ ( j = 1 ) ^ ( r ) s ) stones. Product of two integers Integers allow positive and negative numbers. The two numbers are multiplied just like natural numbers, except we need an additional rule for the signs : ⋅ − + − + − + − + ( displaystyle ( \begin ( array ) ( c cc ) hline cdot & - & + hline - & + & - + & - & + hline end ( array ) ) ) In words, we have : Minus times Minus gives Plus Minus times Plus gives Minus Plus times Minus gives Minus Plus times Plus gives Plus Product of two fractions Two fractions can be multiplied by multiplying their numerators and denominators : z n ⋅ z ′ n ′ = z ⋅ z ′ n ⋅ n ′ ( displaystyle ( \frac ( z ) ( n ) ) cdot ( \frac ( z ' ) ( n ' ) ) = ( \frac ( z cdot z ' ) ( n cdot n ' ) ) ) Product of two real numbers For a rigorous definition of the product of two real numbers see Construction of the real numbers. Product of two complex numbers Two complex numbers can be multiplied by the distributive law and the fact that i 2 = − 1 ( displaystyle mathrm ( i ) ^ ( 2 ) = - 1 ), as follows : ( a + b i ) ⋅ ( c + d i ) = a ⋅ c + a ⋅ d i + b ⋅ c i + b ⋅ d ⋅ i 2 = ( a ⋅ c − b ⋅ d ) + ( a ⋅ d + b ⋅ c ) i ( displaystyle ( \begin ( aligned ) ( a + b , mathrm ( i ) ) cdot ( c + d , mathrm ( i ) ) & = a cdot c + a cdot d , mathrm ( i ) + b cdot c , mathrm ( i ) + b cdot d cdot mathrm ( i ) ^ ( 2 ) & = ( a cdot c-b cdot d ) + ( a cdot d + b cdot c ) , mathrm ( i ) end ( aligned ) ) ) Geometric meaning of complex multiplication A complex number in polar coordinates. Complex numbers can be written in polar coordinates : a + b i = r ⋅ ( cos ⁡ ( φ ) + i sin ⁡ ( φ ) ) = r ⋅ e i φ ( displaystyle a + b , mathrm ( i ) = r cdot ( cos ( \varphi ) + mathrm ( i ) sin ( \varphi ) ) = r cdot mathrm ( e ) ^ ( mathrm ( i ) \varphi ) ) Furthermore, c + d i = s ⋅ ( cos ⁡ ( ψ ) + i sin ⁡ ( ψ ) ) = s ⋅ e i ψ ( displaystyle c + d , mathrm ( i ) = s cdot ( cos ( psi ) + mathrm ( i ) sin ( psi ) ) = s cdot mathrm ( e ) ^ ( mathrm ( i ) psi ) ), from which we obtain : ( a ⋅ c − b ⋅ d ) + ( a ⋅ d + b ⋅ c ) i = r ⋅ s ⋅ ( cos ⁡ ( φ + ψ ) + i sin ⁡ ( φ + ψ ) ) = r ⋅ s ⋅ e i ( φ + ψ ) ( displaystyle ( a cdot c-b cdot d ) + ( a cdot d + b cdot c ) , mathrm ( i ) = r cdot s cdot ( cos ( \varphi + psi ) + mathrm ( i ) sin ( \varphi + psi ) ) = r cdot s cdot mathrm ( e ) ^ ( mathrm ( i ) ( \varphi + psi ) ) ) The geometric meaning is that we multiply the magnitudes and add the angles. Product of two quaternions The product of two quaternions can be found in the article on quaternions. However, it is interesting to note that in this case, a ⋅ b ( displaystyle a cdot b ) and b ⋅ a ( displaystyle b cdot a ) are in general different. Product of sequences The product operator for the product of a sequence is denoted by the capital Greek letter pi ∏ ( in analogy to the use of the capital Sigma ∑ as summation symbol ). The product of a sequence consisting of only one number is just that number itself. The product of no factors at all is known as the empty product, and is equal to 1. Commutative rings Commutative rings have a product operation. Residue classes of integers Main article : residue class Residue classes in the rings Z / N Z ( displaystyle mathbb ( Z ) / N mathbb ( Z ) ) can be added : ( a + N Z ) + ( b + N Z ) = a + b + N Z ( displaystyle ( a + N mathbb ( Z ) ) + ( b + N mathbb ( Z ) ) = a + b + N mathbb ( Z ) ) and multiplied : ( a + N Z ) ⋅ ( b + N Z ) = a ⋅ b + N Z ( displaystyle ( a + N mathbb ( Z ) ) cdot ( b + N mathbb ( Z ) ) = a cdot b + N mathbb ( Z ) ) Rings of functions Main article : ring of functions Functions to the real numbers can be added or multiplied by adding or multiplying their outputs : ( f + g ) ( m ) : = f ( m ) + g ( m ) ( displaystyle ( f + g ) ( m ) : = f ( m ) + g ( m ) ) ( f ⋅ g ) ( m ) : = f ( m ) ⋅ g ( m ) ( displaystyle ( f cdot g ) ( m ) : = f ( m ) cdot g ( m ) ) Convolution Main article : convolution The convolution of the square wave with itself gives the triangular function Two functions from the reals to itself can be multiplied in another way, called the convolution. If ∫ − ∞ ∞ f ( t ) d t < ∞ and ∫ − ∞ ∞ g ( t ) d t < ∞, ( displaystyle int limits _ ( - infty ) ^ ( infty ) f ( t ) , mathrm ( d ) t < infty qquad ( mbox ( and ) ) qquad int limits _ ( - infty ) ^ ( infty ) g ( t ) , mathrm ( d ) t < infty, ) then the integral ( f ∗ g ) ( t ) : = ∫ − ∞ ∞ f ( τ ) ⋅ g ( t − τ ) d τ ( displaystyle ( f * g ) ( t ) ; : = int limits _ ( - infty ) ^ ( infty ) f ( \tau ) cdot g ( t - \tau ) , mathrm ( d ) \tau ) is well defined and is called the convolution. Under the Fourier transform, convolution becomes point-wise function multiplication. Polynomial rings Main article : polynomial ring The product of two polynomials is given by the following : ( ∑ i = 0 n a i X i ) ⋅ ( ∑ j = 0 m b j X j ) = ∑ k = 0 n + m c k X k ( displaystyle left ( sum _ ( i = 0 ) ^ ( n ) a_ ( i ) X ^ ( i ) \right ) cdot left ( sum _ ( j = 0 ) ^ ( m ) b_ ( j ) X ^ ( j ) \right ) = sum _ ( k = 0 ) ^ ( n + m ) c_ ( k ) X ^ ( k ) ) with c k = ∑ i + j = k a i ⋅ b j ( displaystyle c_ ( k ) = sum _ ( i + j = k ) a_ ( i ) cdot b_ ( j ) ) Products in linear algebra There are many different kinds of products in linear algebra ; some of these have confusingly similar names ( outer product, exterior product ) but have very different meanings. Others have very different names ( outer product, tensor product, Kronecker product ) but convey essentially the same idea. A brief overview of these is given here. Scalar multiplication Main article : scalar multiplication By the very definition of a vector space, one can form the product of any scalar with any vector, giving a map R × V → V ( displaystyle mathbb ( R ) \times V \rightarrow V ). Scalar product Main article : scalar product A scalar product is a bilinear map : ⋅ : V × V → R ( displaystyle cdot : V \times V \rightarrow mathbb ( R ) ) with the following conditions, that v ⋅ v > 0 ( displaystyle v cdot v > 0 ) for all 0 ≠ v ∈ V ( displaystyle 0 \not = v in V ). From the scalar product, one can define a norm by letting ∥ v ∥ : = v ⋅ v ( displaystyle \v : = ( sqrt ( v cdot v ) ) ). The scalar product also allows one to define an angle between two vectors : cos ⁡ ∠ ( v, w ) = v ⋅ w ∥ v ∥ ⋅ ∥ w ∥ ( displaystyle cos angle ( v, w ) = ( \frac ( v cdot w ) ( \v cdot w ) ) ) In n ( displaystyle n ) - dimensional Euclidean space, the standard scalar product ( called the dot product ) is given by : ( ∑ i = 1 n α i e i ) ⋅ ( ∑ i = 1 n β i e i ) = ∑ i = 1 n α i β i ( displaystyle left ( sum _ ( i = 1 ) ^ ( n ) alpha _ ( i ) e_ ( i ) \right ) cdot left ( sum _ ( i = 1 ) ^ ( n ) \beta _ ( i ) e_ ( i ) \right ) = sum _ ( i = 1 ) ^ ( n ) alpha _ ( i ) , \beta _ ( i ) ) Cross product in 3 - dimensional space Main article : cross product The cross product of two vectors in 3 - dimensions is a vector perpendicular to the two factors, with length equal to the area of the parallelogram spanned by the two factors. The cross product can also be expressed as the formal determinant : u × v = i j k u 1 u 2 u 3 v 1 v 2 v 3 ( displaystyle mathbf ( u \times v ) = ( \begin ( vmatrix ) mathbf ( i ) & mathbf ( j ) & mathbf ( k ) \u_ ( 1 ) &u_ ( 2 ) &u_ ( 3 ) \v_ ( 1 ) &v_ ( 2 ) &v_ ( 3 ) end ( vmatrix ) ) ) Composition of linear mappings Main article : function composition A linear mapping can be defined as a function f between two vector spaces V and W with underlying field F, satisfying f ( t 1 x 1 + t 2 x 2 ) = t 1 f ( x 1 ) + t 2 f ( x 2 ), ∀ x 1, x 2 ∈ V, ∀ t 1, t 2 ∈ F. ( displaystyle f ( t_ ( 1 ) x_ ( 1 ) + t_ ( 2 ) x_ ( 2 ) ) = t_ ( 1 ) f ( x_ ( 1 ) ) + t_ ( 2 ) f ( x_ ( 2 ) ), \forall x_ ( 1 ), x_ ( 2 ) in V, \forall t_ ( 1 ), t_ ( 2 ) in mathbb ( F ). ) If one only considers finite dimensional vector spaces, then f ( v ) = f ( v i b V i ) = v i f ( b V i ) = f i j v i b W j, ( displaystyle f ( mathbf ( v ) ) = f ( v_ ( i ) mathbf ( b_ ( V ) ) ^ ( i ) ) = v_ ( i ) f ( mathbf ( b_ ( V ) ) ^ ( i ) ) = ( f ^ ( i ) ) _ ( j ) v_ ( i ) mathbf ( b_ ( W ) ) ^ ( j ), ) in which b andb denote the bases of V and W, and v denotes the component of v on b, and Einstein summation convention is applied. Now we consider the composition of two linear mappings between finite dimensional vector spaces. Let the linear mapping f map V to W, and let the linear mapping g map W to U. Then one can get g ∘ f ( v ) = g ( f i j v i b W j ) = g j k f i j v i b U k. ( displaystyle g circ f ( mathbf ( v ) ) = g ( ( f ^ ( i ) ) _ ( j ) v_ ( i ) mathbf ( b_ ( W ) ) ^ ( j ) ) = ( g ^ ( j ) ) _ ( k ) ( f ^ ( i ) ) _ ( j ) v_ ( i ) mathbf ( b_ ( U ) ) ^ ( k ). ) Or in matrix form : g ∘ f ( v ) = G F v, ( displaystyle g circ f ( mathbf ( v ) ) = mathbf ( G ) mathbf ( F ) mathbf ( v ), ) in which the i - row, j - column element of F, denoted by F, is f, and G = g. The composition of more than two linear mappings can be similarly represented by a chain of matrix multiplication. Product of two matrices Main article : matrix product Given two matrices A = ( a i, j ) i = 1... s ; j = 1... r ∈ R s × r ( displaystyle A = ( a_ ( i, j ) ) _ ( i = 1 ldots s ; j = 1 ldots r ) in mathbb ( R ) ^ ( s \times r ) ) and B = ( b j, k ) j = 1... r ; k = 1... t ∈ R r × t ( displaystyle B = ( b_ ( j, k ) ) _ ( j = 1 ldots r ; k = 1 ldots t ) in mathbb ( R ) ^ ( r \times t ) ) their product is given by B ⋅ A = ( ∑ j = 1 r a i, j ⋅ b j, k ) i = 1... s ; k = 1... t ∈ R s × t ( displaystyle B cdot A = left ( sum _ ( j = 1 ) ^ ( r ) a_ ( i, j ) cdot b_ ( j, k ) \right ) _ ( i = 1 ldots s ; k = 1 ldots t ) ; in mathbb ( R ) ^ ( s \times t ) ) Composition of linear functions as matrix product There is a relationship between the composition of linear functions and the product of two matrices. To see this, let r = dim ( U ), s = dim ( V ) and t = dim ( W ) be the ( finite ) dimensions of vector spaces U, V and W. Let U = ( u 1,... u r ) ( displaystyle ( mathcal ( U ) ) = ( u_ ( 1 ), ldots u_ ( r ) ) ) be a basis of U, V = ( v 1,... v s ) ( displaystyle ( mathcal ( V ) ) = ( v_ ( 1 ), ldots v_ ( s ) ) ) be a basis of V and W = ( w 1,... w t ) ( displaystyle ( mathcal ( W ) ) = ( w_ ( 1 ), ldots w_ ( t ) ) ) be a basis of W. In terms of this basis, let A = M V U ( f ) ∈ R s × r ( displaystyle A = M_ ( mathcal ( V ) ) ^ ( mathcal ( U ) ) ( f ) in mathbb ( R ) ^ ( s \times r ) ) be the matrix representing f : U → V and B = M W V ( g ) ∈ R r × t ( displaystyle B = M_ ( mathcal ( W ) ) ^ ( mathcal ( V ) ) ( g ) in mathbb ( R ) ^ ( r \times t ) ) be the matrix representing g : V → W. Then B ⋅ A = M W U ( g ∘ f ) ∈ R s × t ( displaystyle B cdot A = M_ ( mathcal ( W ) ) ^ ( mathcal ( U ) ) ( g circ f ) in mathbb ( R ) ^ ( s \times t ) ) is the matrix representing g ∘ f : U → W ( displaystyle g circ f : U \rightarrow W ). In other words : the matrix product is the description in coordinates of the composition of linear functions. Tensor product of vector spaces Main article : Tensor product Given two finite dimensional vector spaces V and W, the tensor product of them can be defined as a ( 2, 0 ) - tensor satisfying : V ⊗ W ( v, m ) = V ( v ) W ( w ), ∀ v ∈ V ∗, ∀ w ∈ W ∗, ( displaystyle V otimes W ( v, m ) = V ( v ) W ( w ), \forall v in V ^ ( * ), \forall w in W ^ ( * ), ) where V and W denote the dual spaces of V and W. For infinite - dimensional vector spaces, one also has the : Tensor product of Hilbert spaces Topological tensor product. The tensor product, outer product and Kronecker product all convey the same general idea. The differences between these are that the Kronecker product is just a tensor product of matrices, with respect to a previously - fixed basis, whereas the tensor product is usually given in its intrinsic definition. The outer product is simply the Kronecker product, limited to vectors ( instead of matrices ). The class of all objects with a tensor product In general, whenever one has two mathematical objects that can be combined in a way that behaves like a linear algebra tensor product, then this can be most generally understood as the internal product of a monoidal category. That is, the monoidal category captures precisely the meaning of a tensor product ; it captures exactly the notion of why it is that tensor products behave the way they do. More precisely, a monoidal category is the class of all things ( of a given type ) that have a tensor product. Other products in linear algebra Other kinds of products in linear algebra include : Hadamard product Kronecker product The product of tensors : Wedge product or exterior product Interior product Outer product Tensor product Cartesian product In set theory, a Cartesian product is a mathematical operation which returns a set ( or product set ) from multiple sets. That is, for sets A and B, the Cartesian product A × B is the set of all ordered pairs ( a, b ) where a ∈ A and b ∈ B. The class of all things ( of a given type ) that have Cartesian products is called a Cartesian category. Many of these are Cartesian closed categories. Sets are an example of such objects. Empty product The empty product on numbers and most algebraic structures has the value of 1 ( the identity element of multiplication ) just like the empty sum has the value of 0 ( the identity element of addition ). However, the concept of the empty product is more general, and requires special treatment in logic, set theory, computer programming and category theory. Products over other algebraic structures Products over other kinds of algebraic structures include : the Cartesian product of sets the direct product of groups, and also the semidirect product, knit product and wreath product the free product of groups the product of rings the product of ideals the product of topological spaces the Wick product of random variables the cap, cup, Massey and slant product in algebraic topology the smash product and wedge sum ( sometimes called the wedge product ) in homotopy A few of the above products are examples of the general notion of an internal product in a monoidal category ; the rest are describable by the general notion of a product in category theory. Products in category theory All of the previous examples are special cases or examples of the general notion of a product. For the general treatment of the concept of a product, see product ( category theory ), which describes how to combine two objects of some kind to create an object, possibly of a different kind. But also, in category theory, one has : the fiber product or pullback, the product category, a category that is the product of categories. the ultraproduct, in model theory. the internal product of a monoidal category, which captures the essence of a tensor product. Other products A function 's product integral ( as a continuous equivalent to the product of a sequence or as the multiplicative version of the ( normal / standard / additive ) integral. The product integral is also known as `` continuous product '' or `` multiplical ''. Complex multiplication, a theory of elliptic curves. See also Deligne tensor product of abelian categories Iterated binary operation Notes Jump up ^ Here, `` formal '' means that this notation has the form of a determinant, but does not strictly adhere to the definition ; it is a mnemonic used to remember the expansion of the cross product. References Jump up ^ Clarke, Francis ( 2013 ). Functional analysis, calculus of variations and optimal control. Dordrecht : Springer. pp. 9 -- 10. ISBN 1447148207. Jump up ^ Boothby, William M. ( 1986 ). An introduction to differentiable manifolds and Riemannian geometry ( 2nd ed. ). Orlando : Academic Press. p. 200. ISBN 0080874398. Jump up ^ Moschovakis, Yiannis ( 2006 ). Notes on set theory ( 2nd ed. ). New York : Springer. p. 13. ISBN 0387316094. External links Product on Wolfram Mathworld `` Product ''. PlanetMath. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Product_(mathematics)&oldid=805596871 '' Categories : Multiplication Hidden categories : Articles needing additional references from November 2014 All articles needing additional references Talk Contents About Wikipedia Azərbaycanca Беларуская ( тарашкевіца ) ‎ Català Deutsch Ελληνικά Español Esperanto Euskara فارسی Français Ido Íslenska Italiano Македонски Nederlands 日本 語 Norsk Norsk nynorsk Simple English Slovenščina Soomaaliga Svenska ไทย Українська اردو 中文 Edit links This page was last edited on 16 October 2017, at 12 : 23. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: how do you find the product in multiplication
Answer: result of multiplying