# Equilateral Triangle on 3 Concentric Circles

- Author:
- Terry Tam

An equilateral triangle with each of its vertices lying on one of the three concentric circles with radii 8, 15 and 17 respectively.
a) Could you think of how to construct it? Any variants given the point A is fixed?
b) By rotating the largest equilateral triangle at point A by 60 and Cosine Law, find the length of its side and its area

__without using calculator__. c) Could you think of another equilateral triangle with smaller area? How does it look like? Any variants given the point A is fixed?