We need to calculate the area of the cone to know how much paper is needed.
To calculate the cone area we need to know the radius.
We do not have the radio, but we have the volume.
So:
r = √(3×V) / h
r = 4,431cm
Now we calculate the generatrix g.
If we make a lateral projection of the cone, we have a triangle whose height is h = 9cm. The base is the radius r = 4,431cm and the hypotenuse is the generatrix g.
So:
g = √(r ²+ h²)
g = 10.03cm
Finally the area of a cone is given by the formula:
A = pi × r ×(g + r)
A = 201.30 cm²
