sin 2α = 2·sin α·cos α = 2·(±√(1 - cos²α))·cos α = ±2·cos α·√(1 - cos²α) = ±2·(-5/13)·√(1 - (-5/13)²) = ±10/13·12/13 = ±120/169
cos 2α = 2cos²α - 1 = 2·(-5/13)² - 1 = 50/169 - 1 = -119/169
1) sin²α=1-cos²α, отсюда sinα=√(1-cos²α)=√1-25/169=√144/169=(-12/13)
sin2α=2sinα*cosα=2*(-12/13)*(-5/13)=120/169.
2) cos2α=cos²α-sin²α=25/169-144/169=(-119/169)
sin 2α = 2·sin α·cos α = 2·(±√(1 - cos²α))·cos α = ±2·cos α·√(1 - cos²α) = ±2·(-5/13)·√(1 - (-5/13)²) = ±10/13·12/13 = ±120/169
cos 2α = 2cos²α - 1 = 2·(-5/13)² - 1 = 50/169 - 1 = -119/169
1) sin²α=1-cos²α, отсюда sinα=√(1-cos²α)=√1-25/169=√144/169=(-12/13)
sin2α=2sinα*cosα=2*(-12/13)*(-5/13)=120/169.
2) cos2α=cos²α-sin²α=25/169-144/169=(-119/169)