diketahui segitiga ABC dengan AB = 7cm, BC = 5cm, dan AC = 6cm. nilai sin BAC = ....

BC² = AB² + AC² - 2(AB)(AC) cos A
25 = 49 + 36 - 84 cos A
84 cos A = 60
cos A = 5/7

sisi samping = 5
sisi miring = 7
sisi depan = 2akar 6

sin BAC = 2/7 akar 6

s = (1/2) x keliling Δ
s = (1/2) x (7 + 5 + 6)
   = 9 cm
LΔABC = √[s(s - a) (s - b) (s - c)]
             = √[9(9 - 5) (9 - 6) (9 - 7)]
             = √[9 (4) (3) (2)]
             = √(9 x 24)
             = √216 = √(36 x 6)
             = 6√6 cm²

LΔABC = (1/2) b x c x sin A
      6√6 = (1/2) x 6 x 7 x sin A
      6√6 = 21 sin A
      sin BAC = 6√6 / 21