Diameter, radius, circumference, and area

Now, we are in Geometry. There is an important shape we have to see. This is the circle, and it is a very confusing shape. A circle is strange because it has no sides. Now, we start by making two points. Let us put another one, until it is full. You see, it looks like a circle. Now, remember π(3.1415926535)? Well pi is important. But we will explain that later. If you trace a line in the middle, you made the diameter of the circle. Now, if you cut the diameter, you made the radius. We had a perimeter, right? Well, because the circle is so special, its perimeter has a special name. It is called a circumference. Now, let us do an experiment. Try to make the circumference with just the diameter. 1, 2 and 3 are not enough. But, if we take 0.14, we will need 3.14(π)! Now, the formulas for measuring a circumference are so easy, you need to memorize them! The formula for circumference is 3.14(3.14159 for large circumferences)multiplied by the diameter. The formula for area is Pi multiplied by the radius squared. Now, there is a mistake most students do! It is not radius times 2, it is radius multiplied by itself. You can watch the other page about exponents.
Category:Circumference