Question

Тригонометрия, ! вычислите: 1. cos a, tg a, ctg a, если sin a = -5/13, 3п/2 < а < 2п 2. sin a, cos a, ctg a, если tg a = 8/15, п < а < 3п/2

Answer 1

1)
$cos(a) = \sqrt{1 - { \sin(a) }^{2} } = \sqrt{1 - \frac{25}{169} } = \frac{5}{12} \\ \\ \tan( \alpha ) = \frac{ \sin( \alpha ) }{ \cos( \alpha ) } = - \frac{5}{13} \div \frac{5}{12} = - \frac{12}{13} \\ \\ \cot( \alpha ) = \frac{5}{12} \div ( - \frac{5}{13} ) = - \frac{13}{12}$