$$M_y: 2xcos(y) -2xysin(y)-2ycos(x)\\
Nx:4xcos(y)-2xysin(y)-3ycos(x)\\
M_y \neq N_x\\
R = \frac{M_y -N_x}{M} =\frac {-2xcos(y) + ycos(x)}{2xycos(y) - y^2cos(x)}= \frac {-(2xcos(y)-ycos(x)}{2xycos(y)-y^2cos(x)}=\frac{-1}{y}\\
\mu = e^{-\int{\frac{-1}{y}dy}} = e^{\int{\frac{1}{y}}dy} = e^{\int{y}} = y\\
$$
both side times y
$$
(2xy^2cos(y)-y^3cos(x))dx + (2x^2ycos(y) -y^2x^2sin(y)-3y^2sin(x)-5y^4)dy = 0
\phi_{(x,y)} , \phi_x = M, \phi_y = N \\
\phi = \int{M}dx = \int{2xy^2cos(y) - y^3cos(x)}dx\\
= x^2y^2cos(y) - y^3sin(x) + h(y)
\phi_y = 2x^2ycos(y) - x^2y^2sin(y) -3y^2sin(x) + h'(y)= N\\
=2x^2ycos(y)-y^2x^2sin(y)-3y^2sin(x)-5y^4\\
h'(y) = -5y^4\\
h(y) = -y^5\\
\phi = x^2y^2cos(y) - y^3sin(x)-y^5 = C
$$