Question

Решите не используя вольфрам
28sin²x+3sin2x-2=5cos²x

Answer 1

28sin²x+6sinxcosx-2sin²x-2cos²x-5cos²x=0
26sin²x+6sinxcosx-7cos²x=0/cos²x
26tg²x+6tgx-7=0
tgx=a
26a²+6a-7=0
D=36+728=764
a1=(-6-2√191)/52=(-3-√191)/26⇒tgx=(-3-√191)/26⇒x=-arctg(3+√191)/26+πk
a2=(-3+√191)/26⇒tgx(-3+√191)/26⇒x=arctg(-3+√191)/26+πk,k∈z