2sin^x+3,5sin2x-9cos^x=0 2sin^x+7sinxcosx-9cos^x=0 /:cos^x≠0 2tg^x+7tgx-9=0 tgx=z, z∈(-∞; +∞) 2z^+7z-9=0 D=121>0 z=1 z=-9/2 2 случая 1) tgx=1 x=pi/4+pik, k∈Z 2) tgx=-9/2 x=-arctg9/2+pik, k∈Z
