Ctg x = t
t² = t
t²-t =0
t(t-1) =0
t = 0 t -1 =0
t = 1
ctg x= 0 ctg x = 1
x = π/2 x = π/4
13x^2+20x^2=33x^2
Вроде правильно
Возможно так
5х-10-х(квадрат)-4х+3х-12=-22.5-10+20.25+18-13.5-12=-19.8
A+b=360 a=360-b
a/b=5/7 7a=5b 7*(360-b)=5b 2520-7b=5b 2520=12b b=2520/12=210
a=360-b=360-210=150