help me guys please right now

Siku siku di B --> AC sisi miring
Cari penyiku lain (BC)
BC = akar (15^2 - 12^2)
BC = akar (225 - 144)
BC = akar (81)
BC = 9 cm

9 , 12 , 15

L = 9 x 12/2 = 54 cm2

s = 1/2 (9 + 12 + 15) = 1/2 (36) = 18

r dlm
= L/s
= 54/18
= 3 cm