Answer:
1) - 2 / (cos x + sinx)^2.
Step-by-step explanation:
1) I assume you want the derivative of (cos x - sin x) / ( cos x + sin x).
y' = (cosx + sinx)( -sinx - cosx) - (cosx - sinx)(-sinx + cosx)
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(cosx + sinx)^2
= -sinxcosx - cos^2x - sin^2x - sinxcosx - (-sinxcosx+cos^2x+sin^2x-sinxcosx
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(cosx + sinx)^2
= -2sinxcosx - 1 - ( -2sinxcosx + 1 ) / (cosx + sinx)^2
= -2sinxcosx - 1 - ( -2sinxcosx + 1 ) / (cosx + sinx)^2
= - 2 / (cos x + sinx)^2.
