Question 434491
Verify The Equation is an Identity
cosx*cos(-x)-sinx*sin(-x)=1
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cos(-x)=cos(x)  (cos is an even function)
sin (-x)=-sinx   (sin is an odd function)
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cosx*cos(-x)-sinx*sin(-x)
cosx*cosx-(sinx*(-sinx)=cos^2x+sin^2x=1