7sin2x+2=18cos^2x плиз помогите

7sin 2x + 2 = 18cos2 x14sinxcosx+2=36cos²x-1836cos²x-14sinxcosx-20=018cos²x-7sinxcosx-10=018cos²x-7sinxcosx-10cos²x-10sin²x=08cos²x-7sinxcosx-10sin²x=0cosx=(7sinx+-√(49sin²x+320sin²x))/16=(7sinx+-√369sin²x))/16=sinx(7+-3√43)/16ctgx=(7+-3√43)/16x=arcctg(7+-3√43)/16+πk