2sin(2x)+5sin(x)cos(x)−7cos
2
(x)=0
(7cosx-9sinx)*(-cosx)=0(7cosx−9sinx)∗(−cosx)=0
cosx(7cosx-9sinx)=0cosx(7cosx−9sinx)=0
cosx=0 7cosx-9sinx=0
x=π/2 +πn; n∈Z 7cosx=9sinx
7ctgx=9
ctgx=9/7
x=arcctg(9/7)+πn; n∈Z
