[tex]\text{tg }\alpha=0,4\\\frac{5\sin\alpha-\cos\alpha}{2\cos\alpha-10\sin\alpha}:\frac{\cos\alpha}{\cos\alpha}=\frac{5\frac{\sin\alpha}{\cos\alpha}-\frac{\cos\alpha}{\cos\alpha}}{2\frac{\cos\alpha}{\cos\alpha}-10\frac{\sin\alpha}{\cos\alpha}}=\frac{5\text{tg }\alpha-1}{2-10\text{tg }\alpha}=\frac{5\cdot0,4-1}{2-10\cdot0,4}=\frac{2-1}{2-4}=\frac{1}{-2}=-\frac{1}{2}[/tex]
