Решить уравнение  cos14x+ 2sin5xsin9x=0  

[latex]cos14x+ 2sin5xsin9x=0[/latex] [latex]cos14x+ 2* \frac{1}{2}(cos(5x-9x)-cos(5x+9x))=0[/latex] [latex]cos14x+ 2* \frac{1}{2}(cos4x-cos14x)=0[/latex] [latex]cos14x+ cos4x-cos14x=0[/latex] [latex] cos4x=0[/latex] [latex]4x= \frac{ \pi }{2}+ \pi k, [/latex] [latex]k[/latex] ∈ [latex]Z[/latex] [latex]x= \frac{ \pi }{8}+ \frac{\pi k}{4} , [/latex] [latex]k[/latex] ∈ [latex]Z[/latex]