Find the side length, vertex and area of a circle with radius r and inscribed with a regular triangle and a square.

Sine theorem: 2R=a/sinA, A=π/3, a=R* radical number 3.

OD = Rsin & ltOCD & gt=Rsin30 =？ 0.5*R

S =1/2aabsinc =1/2a2sin60 = root number 3*3/4*(R Party).

Pythagorean theorem: A 2 = R 2+R 2

A=R* radical number 2