1
cosx-sin²x=1
cosx-1+cos²x-1=0
cos²x+cosx-2=0
cosx=a
a²+a-2=0
a1+a2=-1 U a1*a2=-2
a1=-2⇒cosx=-2<-1 нет решения<br>a2=1⇒cosx=1⇒x=2πk,k∈z
2
cos2x+sin2x=0/cos2x
1+tg2x=0
tg2x=-1
2x=-π/4+πk,k∈z
x=-π/8+πk/2,k∈z
3
4-5sinxcosx=4cos²x-sin²x
4sin²x+4cos²x-5sinxcosx-4cos²x+sin²x=0
5sin²x-5sinxcosx=0
5sinx(sinx-cosx)=0
sinx=0⇒x=πn,n∈z
sinx-cosx=0/cosx
tgx-1=0
tgx=1
x=π/4+πk,k∈z