frac{ \sin theta }{x} = frac{ cos theta]{ y} sinθx=cosθy
frac{ \sin theta}{\cos theta } = frac{x}{y} sinθcosθ=xy
\tan \theta = x/y tanθ=xy
That's like a right triangle with opposite xx and adjacent yy so
cos theta = frac{\pm y}{sqrt{x^2 + y^2} cosθ=±y√x2+y2
sin theta = \tan \theta \cos theta sinθ=tanθcosθ
\sin theta - cos thetasinθ−cosθ
= tan theta \cos theta - cos theta =tanθcosθ−cosθ
= \cos theta ( \tan theta - 1) =cosθ(tanθ−1)
= frac{\pm y}{sqrt{x^2 + y^2}} (x/y -1) =±y√x2+y2(xy−1)
\sin theta - cos theta = \pm frac {x - y}{sqrt{x^2+y^2}} sinθ−cosθ=±x−y√x2+y2