diketahui tan A = p, maka cos 2 A=

TriGonoMetRi

tan A = y/x = p/1
r = √(y² + x²) = √(p² + 1²) = √(p² + 1)
r² = 1 + p²

cos 2A
= cos² A - sin² A
= x²/r² - y²/r²
= (x² - y²)/r²
= (1 - p²)/(1 + p²) ✔