Which of the following equation is not exact:
1
\(\frac{{dy}}{{dx}} = \frac{{{y^2}\cos x + \cos y}}{{x\sin y - 2y\sin x}}\)
2
\(\frac{{dy}}{{dx}} = - \frac{x}{y}\frac{{\left( {{x^2} + {y^2} - 10} \right)}}{{\left( {{x^2} + {y^2} + 5} \right)}}\)
3
\(\left[ {{y^2}{e^{x{y^2}}} + 4{x^3}} \right]dx + \left[ {2xy{e^{x{y^2}}} - 3{y^2}} \right]dy = 0\)
4
2 sin y2 dx + xy cos y2 dy = 0