\
Isosceles triangle is inscribed in a circle.
\ be the radius of the circle.
be the base of the triangle.
Observe the figure.
\From the figure, height of the triangle is .
From the pythagorean theorem,
\The area of the triangle is .
The area of the triangle is maximum when its first derivative becomes zero.
\Apply derivative on each side with respect to .
\
Equate to zero.
The general solution for a quadratic equation is .
Here can not benegative.
Hence .
Substitute in
.
Therefore the height of the triangle is .
Substitute in
.
Therefore the base of the triangle is .
\
The height of the triangle is .
The base of the triangle is .