Найти: sinx -?; sin2x-?
ctg (3π/2 + x)-?
sin^2 x = 1 - cos^2 x = 1 - (-20/29)^2 = 1 - 400/841 = 441/841
sin x = +sqrt(441/841) = 21/29
[m]\sin 2x = 2\sin x \cdot \cos x = 2 \cdot \frac{21}{29}(-\frac{20}{29}) = - \frac{2 \cdot 21 \cdot 20}{29 \cdot 29} = -\frac{840}{841}[/m]
[m]ctg(\frac{3\pi}{2} + x) = -tg(x) = -\frac{\sin x}{\cos x} = -\frac{21}{29} : (-\frac{20}{29}) = \frac{21}{29} \cdot \frac{29}{20} = \frac{21}{20}[/m]