Question

(sin a-sin b)/(cos a+cos b), если a-b=Π/2

Answer 1

$a-b=\frac{\pi}{2}\quad \Rightarrow \quad a=\frac{\pi}{2}+b\\\\ \frac{sina-sinb}{cosa+cosb} = \frac{sin(\frac{\pi}{2}+b)-sinb}{cos(\frac{\pi}{2}+b)+cosb} = \frac{cosb-sinb}{-sinb+cosb} =1$