Question

Find the area of an inqulateral tringle in scribed in the circle

Answer 1

let r is the radius of circle
use cosine formula
cos120=(r^2+r^2-x^2)/2r^2 {where x is side length of equilatral triangle

-1/2=(2r^2-x^2)/2r^2

-r^2=2r^2-x^2
x=r root3
now area of triangle=(root3/4) x (r root3)^2=3root3/4.r^2