Diketahui cos a=12/13 a sudut lancip tentukaan nilai sin 2a dan cos 2a°

cos A = 12/13, x = 12 dan r = 13
y² = r² - x² = 13² - 12² = 25
y = 5
sin A = y/r = 5/13
sin(2A) = 2 sinA cosA = 2(5/13)(12/13) = 120/169
cos(2A) = 2 cos²(A) - 1 = 2(12/13)² - 1 = 119/169