28sin^2x+3sin2x-2=5cos^2x буду крайне

28sin²x+6sinxcosx-2sin²x-2cos²x-5cos²x=0/cos²x
26tg²x+6tgx-7=0
tgx=a
26a²+6a-7=0
D=36+364=400
a1=(-6-20)/52=-1/2⇒tgx=-1/2⇒x=-arctg0,5+πn,n∈z
a2=(-6+20)/52=7/26⇒tgx=7/26⇒x=arctg7/26+πk,k∈z