A sphere is a perfectly round 3D solid where every point on its surface is the same distance (the radius) from its center.
1. Surface Area (S.A) of a sphere with radius r covers exactly the area of 4 great circles of the same radius.
2. Area of one great circle = πr²
3. Surface Area (S.A) = 4 × πr² = 4πr²
4. For a sphere, SA = CSA = TSA because it has no separate base.