Materi : Aturan Sinus dan Cosinus Pada segitiga ABC diketahui sisi-sisinya AB = 4 cm, BC = 5 cm dan AC = 6 cm. Tentukan nilai sinus ∠C !

cosC = (6^2 + 5^2 - 4^2)/2×6×5
cosC = (36+25-16)/60
cosC = 45/60
cosC = 3/4

sin^2 C = 1 - cos^2 C = 1- (3/4)^2 = 1- 9/16
sin^2 C = (16-9)/16
sin^2 C = 7/16
sinC = akar(7/16)
sinC = 1/4 akar7

Bab Trigonometri
Matematika SMA Kelas XI

aturan cosinus
cos C = (BC² + AC² - AB²)/(2 x BC x AC)
cos C = (5² + 6² - 4²)/(2 x 5 x 6)
cos C = (25 + 36 - 16)/(60)
cos C = 45/60
cos C = 3/4 = x/r

Tripel Pitagoras
y = √(r² - x²)
y = √(4² - 3²)
y = √(16 - 9)
y = √7

sin C = y/r
sin C = (√7)/4
sin C = (1/4) √7