Compute the surface area of a sphere of radius R Hint use th

Solution

consider any circle at a distance x from centre of sphere   :

circumgference of circle - 2* sqrt[R² - x²]dx

integrate it using substitution

put x = r sin

dx = r cos d

:   2* *(R cos)*(R* cos) d

: R² [ 1 + cos2 ] d

: R² [ + sin2/2 }

put limits of from 0 to /2 and multiply it by 2 in end

: 2R² [2 ]

4r²   answer !!!