tg\alpha=4
\frac{sin\alpha}{cos\alpha}=4
sin\alpha=4cos\alpha
{\frac{sin\alpha+cos\alpha}{sin\alpha-cos \alpha}=\frac{sin\alpha+cos\alpha}{4cos\alpha-cos \alpha}=\frac{sin\alpha+cos\alpha}{3cos \alpha}=\frac{sin\alpha}{3cos \alpha}+\frac{cos\alpha}{3cos \alpha}=\frac{1}{3}\cdot \frac{sin\alpha}{cos\alpha}+\frac{1}{3}=\frac{1}{3}\cdot 4+\frac{1}{3}=\frac{4}{3}+\frac{1}{3}=\frac{5}{3}=1\frac{2}{3}}