[tex]\displaystyle\bf\\\frac{Sin\alpha +tg\alpha }{tg\alpha } =\frac{Sin\alpha }{tg\alpha } +\frac{tg\alpha }{tg\alpha } =\frac{Sin\alpha }{\frac{Sin\alpha }{Cos\alpha } } +1=\frac{Sin\alpha \cdot Cos\alpha }{Sin\alpha } +1=Cos\alpha+1\\\\\\Cos\alpha +1=1+Cos\alpha[/tex]