diketahui Δ ABC dengan AC = 10 cm ∠ABC=45° dan ∠BAC = 30°. Panjang BC =...

dik, AC = 10 cm
sudut ABC = 45°
sudut BAC = 30°
dit, BC?
penyelesaian:
sin 45° = AC/AB
½√2 = 10/AB
AB = 10/(½√2)
AB = 10 × 2/√2
AB = 20/√2 × √2/√2
AB = 20√2/2
AB = 10√2 cm

BC = √(AB² - AC²)
BC = √{(10√2)² - 10²}
BC = √{(100 × 2) - 100}
BC = √(200 - 100)
BC = √100
BC = 10 cm