Question

formula for radius of an isosceles triangle

Answer 1

These formulae for any type of triangles

Inradius = (area of triangle)/(semi perimeter)

Semiperimeter=(sum of all 3sides)/2

Circumradius= abc/ 4(area of triangle)

a, b, c are the sides of triangle

Hope,it helps you

Answer 2

Let us assume an isosceles triangle an isosceles triangle with sides a, a and b, then we have the following formulas

(1) Circumradius of isosceles triangle, R = a/ 2* SinA

                              = $\frac{a^2}{\sqrt{4a^2 - b^2}}$

(2) Inradius of isosceles triangle, r = $\frac{b}{2} \sqrt{}\frac{2a - b}{2a + b}$    

In this way we can draw both the circles and the picture of the circles is in the attachment. Note that R is always greater than the r.