Help me! Matematika OKE?

maksudnya cari panjang BC?

BC = √(12² + 9²)
BC = √(144 + 81)
BC = √225
BC = 15 cm

BC² = (AC²+AB²)
BC = √(AC²+AB²)
BC = √(9² + 12²)
BC = √(81 + 144)
BC = √225
BC = 15 cm