$$\text { Find the area of the surface obtained by rotating the circle } x ^ { 2 } + y ^ { 2 } = 9 ^ { 2 } \text { about the line } y = 9 \text {. }$$

Short Answer

$$\text { Find the area of the surface obtained by rotating the circle } x ^ { 2 } + y ^ { 2 } = 9 ^ { 2 } \text { about the line } y = 9 \text {. }$$