Jika sin x=4/5 Tentukan nilai cos 2x dan tan 2x

Halo akan saya coba jawab. Diketahui sin x = 4/5 ingat sin x = y/r (depan per miring) maka x (samping) = √(r² - y²) -> teorema phytagoras x = ±√(5² - 4²) x = ± √(25 - 16) x = ±√9 x = ±3 ✓ ambil x = 3 maka cos x = x/r (samping per miring) = 3/5 tan x = y/x (depan per samping) = 4/3 maka cos 2x = cos² x - sin² x cos 2x = (3/5)² - (4/5)² cos 2x = 9/25 - 16/25 cos 2x = -7/25 ✓ tan 2x = (2 tan x)/(1 - tan² x) tan 2x = (2 × 4/3)/(1 - (4/3)²) tan 2x = (8/3)/(1 - 16/9) tan 2x = (8/3)/(-7/9) tan 2x = 8/3 × -9/7 tan 2x = 8/7 (-3) tan 2x = -24/7 ✓