If 2 sides of a triangle are described by 2 vectors a and b , how does one work out what vector defines the third side ?
If a , b and c represent the vectors determined by the sides of a triangle ABC -LRB- taken in order -RRB- , then how I prove that | b × c | = | c × a | = | a × b | and hence ? How do I show that -LRB- a-b -RRB- × -LRB- a + b -RRB- = 2 -LRB- a × b -RRB- ?