6. Запишите, чему равен: 1) sin (90° – α); 2) cos (90° – α); 3) tg (90° - α); 4) ctg (90° -α).

1) $$\sin (90^\circ - \alpha) = \cos \alpha$$

2) $$\cos (90^\circ - \alpha) = \sin \alpha$$

3) $$\tan (90^\circ - \alpha) = \cot \alpha$$

4) $$\cot (90^\circ - \alpha) = \tan \alpha$$