Sina+cosa/ корень из 2 cos(pi/4-a)

[latex] \frac{sin \alpha +cos \alpha }{ \sqrt{2}*cos( \frac{pi}{4}- \alpha )} }= \frac{sin \alpha +cos \alpha }{ \sqrt{2}*(cos \frac{pi}{4}*cos \alpha +sin \frac{pi}{4}*sin \alpha) }= \frac{sin \alpha +cos \alpha }{ \sqrt{2}*(sin \alpha +cos \alpha ) }= \frac{1}{ \sqrt{2} } [/latex]