Δ BSC- равнобедренный:
BC=2L*sin15 ° =8sin15 °
Δ BDC- прямоугольный, ∠ BCD=90 °
BD^2=DC^2+BC^2=4^2+64sin^215 °=16*(1+2*2sin^215 ° )=
=16*(1+2*(1-cos30 ° ))=16*(3-sqrt(3))
BD=4sqrt(3-sqrt(3))
BO=2sqrt(3-sqrt(3)) ⇒ R=2sqrt(3-sqrt(3))
SO^2=SB^2-BO^2=4^2-(2sqrt(3-sqrt(3)))^2=16-4*(3-sqrt(3))=4*(1+sqrt(3))
H=2*sqrt(1+sqrt(3))
V=(1/3)π*R^2*H=(1/3)*π*(2sqrt(3-sqrt(3)))^2*2*sqrt(1+sqrt(3))=...
S_(бок)=π*R*L=π*(2sqrt(3-sqrt(3))) * 4=...