tlong nmer 23 dan caranya ya

luas = 1/2 a.t
luas = 1/2.AB.BC sin B
luas = 1/2.12.8.sin 45°
luas = 1/2.12 .8 .(1/2)√2
luas = 6.4√2
luas = 24√2....(b)

LuasΔ = 1/2.a.c.sinβ
           = 1/2.8.12.sin45
           = 48.1/2√2
           = 24√2