Circle Theorems

Circumference = Pi x diameter.

e.g. What is the circumference of a circle with a diameter of 4cm? Give your answer to two decimal places.

Practice Question: Work out the circumference of the circle when its radius is 6mm. Give your answer to two decimal places.

Area = Pi x radius squared.

e.g. What is the area of a circle with a radius of 3cm? Give your answer to two decimal places.

Practive Question: Work out the area of a circle with a diameter of 14mm. Give your answer to two decimal places.

Remember: Sometimes exam questions could ask for the circumference of a circle but give you the radius instead of the diameter.

Angles in a Cyclic Quadrilateral add upto 180 degrees.

E.g. a + c = 180 degrees.

b + d = 180 degrees.