Question

Алгебра 11 класс
25 баллов ​

Answer 1

Ответ:

$1)\ \ sinx=-0,8\\\\180^\circ <x<270^\circ \ \ \ \Rightarrow \ \ \ cosx<0\ \ ,\ \ cosx=-\sqrt{1-sin^2x}\\\\cosx=-\sqrt{1-0,64}=-\sqrt{0,36}=-0,6\\\\\\2)\ \ sina=-\dfrac{5}{\sqrt{26}}\\\\a\in \Big(\ \pi \ ;\ \dfrac{3\pi}{2}\ \Big)\ \ \ \Rightarrow \ \ \ cosa<0\ ,\ tga>0\ \ ,\ \ tga=\dfrac{sina}{cosa}=\dfrac{sina}{-\sqrt{1-sin^2a}}\\\\\\tga=\dfrac{-\dfrac{5}{\sqrt{26}}}{-\sqrt{1-\dfrac{25}{26}}}=\dfrac{5}{\sqrt{26}\cdot \sqrt{\dfrac{1}{26}}}=5$