# Circle Theorems

##### Age 14 to 16Challenge Level

This page contains a geoboard environment that can be used for circle work as well as well as other problems (such as Pick's Theorem ). There are also a number of problems that introduce circle theorems, all of which have a special version of the interactivity to support them. By working on the problems learners will develop a better understanding of some of the angle properties of circles.

Virtual Geoboard
A generic environment for supporting work on geometry and area can be found here .

Triangles in Circles
This problem offers a good preparation for the problems Subtended angles and Right angles which lead towards the circle theorems.
Students will only need to know that the angles round a point add up to 360 ° and how to calculate angles in isosceles triangles.
"How many different triangles can you make which consist of the centre point and two of the points on the edge? Can you work out each of their angles?"

Subtended Angles