Hello,

Problem:

I can't find my mistake when solving the surface area of a sphere.

Description of the sphere:

Given a sphere of radius centered at the origin. There is a circle at distance from the origin which has a radius of which is inscribed in the sphere

Description of the problem:

I was solving both the volume and area of a sphere. At first I calculated the volume of the sphere in the following approach:

(Area of the circle)

Where it calculates the area of every circle and multiplicates by the differential. No problems here.

Now I wanted to do the same for the surface area, but using the circumference length instead, therefore:

(Length of the circumference)