Lateral area of a frustum of a regular pyramid
$$S_{son} = \frac{S1-S2}{cos(\phi)}$$
S_lat - lateral area
S1, S2 - areas of lower and upper bases
φ - angle between the slant edge and the lower base
S1, S2 - areas of lower and upper bases
φ - angle between the slant edge and the lower base
Find
It is known that:
= 