[tex]\begin{gathered} 2\tan \theta-3\cos \theta=2\frac{\sin\theta}{\cos\theta}-3\cos \theta \\ 2\frac{\sin\theta}{\cos\theta}-3\cos \theta=2\frac{\sin\theta}{\cos\theta}-3\frac{\cos ^2\theta}{\cos \theta} \\ 2\frac{\sin\theta}{\cos\theta}-3\frac{\cos^2\theta}{\cos\theta}=\frac{2\sin \theta-3\cos ^2\theta}{\cos \theta} \\ \frac{2\sin\theta-3\cos^2\theta}{\cos\theta}=\frac{2\sin \theta-3(1-\sin ^2\theta_{})}{\cos \theta} \\ \frac{2\sin\theta-3(1-\sin^2\theta_{})}{\cos\theta}=\frac{3\sin ^2\theta+2\sin \theta-3}{\cos \theta} \end{gathered}[/tex]
