Question

cosa-cosb/sina+sinb = если a-b = 90 градусов.

Answer 1

$\frac{Cos\alpha-Cos\beta}{Sin\alpha+Sin\beta }=\frac{-2Sin\frac{\alpha+ \beta }{2}*Sin\frac{\alpha-\beta}{2}}{2Sin\frac{\alpha+\beta}{2}*Cos\frac{\alpha-\beta}{2}}=\frac{-Sin\frac{90^{0} }{2} }{Cos\frac{90^{0} }{2} }=\frac{-Sin45^{0} }{Cos45^{0} } =\frac{-\frac{\sqrt{2} }{2} }{\frac{\sqrt{2} }{2}}=-1$