Explanation:
> find the angle of center circle:
cos~¹ 5/(5+12) = cos~¹ 5/17 = 72°
so the sector area of the shaded
region =
(360-72)/360 × 3.14 × 5²
= 288/360 × 78.5
= 62.8
> the height of triangle (red Line) =
4×tan 72° = 4× 3.078 = 12.31
the height of pyramid (green
Line) = √12.31²-8.5² =√74.16
= 8.61
so the volume of pyramid =
⅓×(17×8)×8.61 = 390.32