Stage: 4 Challenge Level: 
The centre of the larger circle is at the midpoint of one side of an equilateral triangle and the circle touches the other two sides of the triangle. A smaller circle touches the larger circle and two sides of the triangle. If the small circle has radius 1 unit find the radius of the larger circle.
Isosceles triangles. Right angled triangles. Angle properties of shapes. Pythagoras' theorem. Circles. Reflections. Perpendicular lines. Compound transformations. Rotations. Tangents.
Published April 2001.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk
