Two solid right circular cones and radii r1 and r2 and have the same height h, they are method and react into a cylinder of same height. Show that the radius of the base of cylinder is √[r1]°2+[r2]°2^3.

Answer 1

Check for typos please.
If you mean merged, same total volume, then with the same height, the base areas add up to the original.
pi R^2 = pi r1^2 + pi r2^2
R2 = sqrt( r1^2 + r2^2)