Question

найдите cos²a ,если tga=
$\sqrt{3}$
​

Answer 1

Ответ:

$tgA=\sqrt3\\\\1+tg^2A=\dfrac{1}{cos^2A}\ \ \ \Rightarrow \ \ \ cos^2A=\dfrac{1}{1+tg^2A}=\dfrac{1}{1+3}=\boxd{\dfrac{1}{4}\ }\\\\\\\star \ \ cosA=\pm \dfrac{1}{2}\ \ \star$