Question

Подскажите как сделать А14

Answer 1

$\displaystyle \frac{cos(-135)+sin(-120)-cos(-120)}{tg^2690+ctg^2(-30)}=$

$\displaystyle = \frac{cos(-(180-45))+sin(-(180-60))-cos(-(180-60))}{tg^2(360+360-30)+ctg^2(-30)}=$

cos - четная sin-нечетная

$\displaystyle \frac{cos( \pi -45)-sin( \pi -60)-cos( \pi -60)}{(-tg30)^2+(-ctg30)^2}=$

$\displaystyle = \frac{-cos45-sin60+cos60}{tg^230+ctg^230}=$

$\displaystyle = \frac{ -\frac{ \sqrt{2}}{2}- \frac{ \sqrt{3}}{2}+ \frac{1}{2}}{ \frac{1}{3}+3}= \frac{1- \sqrt{2}- \sqrt{3}}{2}* \frac{3}{10}$