cos^2 x - sin^2x + cosx*sinx=0 | :cos^2 x
1-tg^2 x +tgx=0
tgx=y
y^2-y-1=0
y1=1+sqrt (5) \ 2
y2=1-sqrt (5) \ 2
x= arctg(y) +пn
cos^2 x - sin^2x + cosx*sinx=0 | :cos^2 x
1-tg^2 x +tgx=0
tgx=y
y^2-y-1=0
y1=1+sqrt (5) \ 2
y2=1-sqrt (5) \ 2
x= arctg(y) +пn