cari rumus luas segitiga menggunakan trigonometri. lalu hitung luas segitiga dibawah ini. 1. A = 60° b = 10 cm c = 8cm 2. a = 7cm b = 8cm. c = 9cm

1) L = 1/2 × b × c × sin a
= 1/2 × 10 × 8 × sin 60°
= 1/2 × 10 × 8 × 1/2 akar 3
= (20 akar 3) cm^2
2) S = 1/2 × ( a + b + c )
= 1/2 × ( 7 + 8 + 9 )
= 1/2 × 24
= 12 cm
L = akar [S×(S-a)(S-b)(S-c)]
= akar [12×(12-7)(12-8)(12-9)]
= akar [12×5×4×3]
= akar 720
= akar (144×5)
= (12 akar 5) cm^2