4. ∠A = 30°, ∠C = 75°, a = 8

∠B = 180° − 30° − 75° = 75°.

По теореме синусов: \(b=8\cdot\frac{\sin75°}{\sin30°}\approx15{,}45\), \(c=8\cdot\frac{\sin75°}{\sin30°}\approx15{,}45\).

Ответ: ∠B = 75°, b ≈ 15,45, c ≈ 15,45.