5/cos^2 x +7/sin(5p/2-x) +2=0

Решите задачу:

$\frac{5}{cos^2x} + \frac{7}{sin(\frac{5\pi }{2}-x)} +2=0\\\\sin(\frac{5\pi }{2}-x)=cosx\; \; \Rightarrow \; \; \frac{5}{cos^2x} + \frac{7}{cosx} +2=0\, |\cdot cos^2x\ne 0\\\\ \frac{5+7cosx+2cos^2x}{cos^2x} =0\; ,\; cosx\ne 0\\\\2cos^2x+7cosx+5=0\\\\D=9\; ,\; (cosx)_1=-\frac{5}{2}\; \; net\; reshenij\\\\(cosx)_2=-1\; ,\; x= \pi +2\pi n,\; n\in Z\\$