1
36tgx-27=26tgx+104
10tgx=131
tgx=13,1
x=arctg13,1+πn,n∈z
2
cosx*(cosx-6sinx)=0
cosx=0⇒x=π/2+πn,n∈z
cosx-6sinx=0/cosx
1-6tgx=0⇒tgx=1/6⇒x=arctg1/6+πk,k∈z
3
6cos²x-1=cosx
cosx=a
6a²-a-1=0
D=1+24=25
a1=(1-5)/12=-1/3⇒cosx=-1/3⇒x=+-(π-arccos1/3)+2πn,n∈z
a2=(1+5)/12=1/2⇒cosx=1/2⇒x=+-π/3+2πk,k∈z