Hitunglah luas ∆ RST, jika diketahui r=20cm, s=37cm, dan t=51cm

$=(20+37+51)/2
= 108/2
= 54
luas = akar($.($-r)($-s)($-t))
= akar(54.(54-20)(54-37)(54-51))
= akar(54.24.17.3)
= akar(2.3^3.2^3.3.17.3)
= akar(2^4.3^4.17.3)
= 2^2.3^2akar(51)
= 4.9akar(51)
= 36akar(51) cm^2