<span>tg(a) + ctg(a) = 3
</span>(tg(a) + ctg(a))² = 9
tg²(a) + 2*tg(a)*ctg(a) + ctg²(a) = 9
tg²(a) + ctg²(a) = 9 - 2*tg(a)*ctg(a)
tg²(a) + ctg²(a) = 9 - 2 = 7
--------------------------------- известно: tg(a)*ctg(a) = 1
(9/4+15/8)*9/11-7/2=33/8*9/11-7/2=27/8-7/2=27-28/8=-1/8
1/4*1/2*1/4=1/32 ну вроде так
Да.
(-7^2) = -7*-7=49.
<span>√49 = 7</span>
Cos x/2 = -1/2
x/2 = ± arccos1/2 + 2pin
x/2 = ± pi/3 + 2pin
x = <span>± 2pi/3 + 2pin</span>