Circle Theorems

Circle theorems!

The joys of circle theorems have finally landed on this page!!!
I always find circle theorems one of the most easiest, along with Pythagorean theory the most easiest of the theorems to learn!
Today we are going to go through the basics of them!!

Lets take a look at a basic labelled diagram!

• The radius is the red line. We know it is the radius because the radius is centre to edge!
• The diameter is the blue line. We know this because the diameter is edge to edge!
• Also we know that the full circle around (the black circle) is the circumference.

The only equations we need to know for this are the area and circumference equations.

Area = πR^{2 = Pi x R x 2} 

Circumference= π x D 

• If we know the radius is 4 then we can work out the diameter is 8.
• If we know the diameter is 6 we can work out the radius is 3 

These are CALCULATOR equations, unless you are a wizz and can do this in your head!!! 

1.A circle has a Diameter of 8, what is the area?

π x r x 2 

In a calculator write π x 4 x 2 

You should get the answer of 50.27 rounded to 2dp.

2. A circle has a radius of 16, what is the Circumference?

π x D

In a calculator write π x 32 

You should get the answer of 100.53 rounded to 2dp

This is all for this blog!! Look out for Circle theorems #2 

We will be looking at labelling the different parts of a circle!!!

 

Thank you for learning :)