Tolong bantu di jawab ya kaka pake cara ditulis rapi. Makasih :)

a) AC / sin C = BC / sin B
20 / sin 60 = BC / sin 45
20 / (1/2√3) = BC / (1/2✓2)
10✓2 = 1/2✓3 BC
BC = (20✓2)/✓3
= (20✓6)/3 cm
b) L∆ = 1/2 x AC x BC x sin 75
= 1/2 x 20 x (20√6)/3 x 0,97
= 16,33 x 10 x 0,97
= 158,4 cm²