Question

Найдите tg a, если cos a= -2/5

Answer 1

$1 + \tan {}^{2} ( \alpha ) = \frac{1}{ \cos {}^{2} ( \alpha ) }$
$\tan {}^{2} ( \alpha ) = \frac{1}{ \cos {}^{2} ( \alpha ) } - 1$
$\tan {}^{2} ( \alpha ) = \frac{1}{ \frac{ 4}{25} } - 1$
$\tan {}^{2} ( \alpha ) = \frac{ 25}{4} - \frac{4}{4}$
$\tan {}{} ( \alpha ) = \frac{ \sqrt{21} }{2}$Ответ:
$\tan( \alpha ) = \frac{ \sqrt{21} }{2}$