### Some(?) of the Parts

A circle touches the lines OA, OB and AB where OA and OB are perpendicular. Show that the diameter of the circle is equal to the perimeter of the triangle

### Rotating Triangle

What happens to the perimeter of triangle ABC as the two smaller circles change size and roll around inside the bigger circle?

### Pericut

Two semicircle sit on the diameter of a semicircle centre O of twice their radius. Lines through O divide the perimeter into two parts. What can you say about the lengths of these two parts?

# LOGO Challenge 11 - More on Circles

##### Stage: 3 and 4 Challenge Level:

The result of the substitutions 314 and 100 into the two procedures produce the same circles.

This can be confirmed by rearranging the formula: $C=\pi d$.

Experimentation with this relationship through investigating the two procedures and creating circles which touch and/or which are related by particular enlargements all support familiarity with the relationship between the diameter and circumference of any circle.