The semivertical angle of a cone is 45^ . If the height of the cone is 20.025 ~cm , then the approximate value of its lateral surface area (in sq. cm ) is

Step-by-step solution

In A O B , aligned & 45^ = r h & 1= r h r=h aligned and l^2=r^2+h^2 aligned & l= h^2+h^2 & l= 2 h^2 = 2 h aligned [ r=h] Lateral surface area array lll (S) & = r l & & = h 2 h & S & = 2 h^2 & [ h=20.025 ~cm ] & = 2 (20.025)^2 & & = 2 401 & S & =401 2 & array Hence, option (a) is correct.