The approximate change in the total surface area of a right circular cone when the radius 'r' remains constant while altitude h changes by `'alpha'` is

Options

A. `(pirhalpha)/(sqrt(r^(2)+h^(2)))`
B. `(pirh)/(sqrt(r^(2)-h^(2)))`
C. `(pirhalpha)/(sqrt(r^(2)-h^(2)))`
D. `(pihalpha)/(sqrt(r^(2)+h^(2)))`

Answer

A