Dik: segitiga PQR dengan PQ=4cm,QR=5cm dan PR=7cm hitunglah setengah keliling PQR dan hitunglah luas segitiga PQR

1/2 K = 1/2 ( 4+5+7) = 1/2 (16) = 8

L =√s(s-a)(s-b)(s-c)
cari s
s = 4+5+7/2= 16/2 = 8

L= √8(8-4)(8-5)(8-7)
L = √8(4)(3)(1)
L = √96
L = √16*6
L = 4√6

s = 1/2 keliling = 1/2 (4 + 5 + 7) = 1/2 (16) = 8 cm

PQ = 4 cm = r
QR = 5 cm = p
PR = 7 cm = q
Luas = √(s (s - r) (s - p) (s - q))
= √(8 (8 - 4) (8 - 5) (8 - 7))
= √(8 (4) (3) (1))
= √96
= 4√6 cm^2