Question

ПОМОГИТЕ ДОПИСАТЬ ФОРМУЛЫ

Answer 1

$tg\alpha\cdot ctg\alpha=1\\\sin^2\alpha=1-\cos^2\alpha\\\cos^2\alpha-1=-\sin^2\alpha\\1-\sin^2\alpha=\cos^2\alpha\\1-ctg^2\alpha=?\\\sin^2\alpha-1=-\cos^2\alpha\\tg\alpha=\frac{\sin\alpha}{\cos\alpha}$