Cos2x+2,5sin2x+5cos^2x=0

Question

Cos2x+2,5sin2x+5cos^2x=0

Answer 1

Сos²x-sin²x+5sinx*cosx+5cos²x=0/cos²x
tg²x-5tgx-6=0
tgx=a
a²-5a-6=0
a1+a2=5 U a1*a2=-6
a1=-1⇒tgx=-1⇒x=-π/4+πn,n∈z
a2=6⇒tgx=6⇒x=arctg6+πk,k∈z