Sin theta /x = cos theta /y then sin theta - cos theta=?

1 Answer
Apr 19, 2018

If frac{ \sin theta }{x} = frac{ cos theta]{ y} sinθx=cosθy then \sin theta - cos theta = \pm frac {x - y}{sqrt{x^2+y^2}} sinθcosθ=±xyx2+y2

Explanation:

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=±yx2+y2

sin theta = \tan \theta \cos theta sinθ=tanθcosθ

\sin theta - cos thetasinθcosθ

= tan theta \cos theta - cos theta =tanθcosθcosθ

= \cos theta ( \tan theta - 1) =cosθ(tanθ1)

= frac{\pm y}{sqrt{x^2 + y^2}} (x/y -1) =±yx2+y2(xy1)

\sin theta - cos theta = \pm frac {x - y}{sqrt{x^2+y^2}} sinθcosθ=±xyx2+y2