3+2sin x cos x = 4 sin² x

4sin²x-3sin²x-3cos²x-2sinxcosx=0/cos²x
tg²x-2tgx-3=0
tgx=a
a²-2a-3=0
a1+a2=2 U a1*a2=-3
a1=-1⇒tgx=-1⇒x=-π/4+πn,n∈z
a2=3⇒tgx=3⇒x=actg3+πk,k∈z