Equilateral triangle ABC is inscribed in circle D. If the altitude of triangle ABC is 15, what is the length of the circle's radius?

Answer 1

Cutting the triangle in half; side a=?

b=15

c=?

Each angle α, β, and γ=60°.

We want side c of triangle 30°, 120°, 30°. Cutting this triangle in half; side a=5;

So a/sinα=b/sinβ=c=5/sin30°=10=r.