23. a) oblicz sin α, gdy cos α = 3/4 b) oblicz cos α, gdy sin α = -0,8 c) oblicz sin α, gdy cos α = - 1/5 i 180° < α < 360° d) oblicz cos α, gdy sin α = 2/3 i - 270° < α < -180° Proszę o wyjaśnienie

a) sin^{2}α + cos^{2}α = 1 sin^{2}α + (3/4)^{2} = 1 sin^{2}α + 9/16 = 1 sin^{2}α = 1 - 9/16 sin^{2}α = 7/16 sinα = √7/4 b) (-0,8)^{2} + cos^{2}α = 1 0,64 + cos^{2}α = 1 cos^{2}α = 1 - 0,64 cos^{2}α = 0,36 cosα = 0,6 c) sin^{2}α + (-1/5)^{2} = 1 sin^{2}α + 1/25 = 1 sin^{2}α = 1 - 1/25 sin^{2}α = 24/25 sinα = √24/5 d) (2/3)^{2} + cos^{2}α = 1 4/9 + cos^{2]α = 1 cos^{2}α = 1 - 4/9 cos^{2}α = 5/9 cosα = √5/3