S = 2S₁
S = 2 * 1/2 absinα = absinα
S_{A₁B₁C₁D₁} = 1/2A₁C * B₁D * sinα

Վ. 350

S = ?
S = 2S₁ = 2 * 1/2 absinα = absinα = 12 * 12 * √3/2 = 12 * 6 * √3 = 72√3

Վ. 351

S = 8√2
a = ?
S = a² * sin45^o
8√2 = a² * √2/2
a² = 8√2 : √2/2 = 8√2 * 2/√2 = 16
a = 4