Question 889760
[Sin^3(x)-cos^3(x)] / [sin(x)-cos(x)] = 1+sinx.cosx
we know  that a^3-b^3=(a-b)(a^2+b^2+ab)   using same identity 
sin^3 x- cos^3 x=(sin x-cos x)(sin^2 x+ cos^2 x+cos x sin x) 

we know sin^2 x+cos^2=1   by substitution  
sin^3 x- cos^3 x=(sin x-cos x)(1+cos x sin x) 
[Sin^3(x)-cos^3(x)] / [sin(x)-cos(x)] = (sin x-cos x)(1+cos x sin x)/(sin x- cos x)   by cancelling (sin x- cos x) from numerator and denominator 
[Sin^3(x)-cos^3(x)] / [sin(x)-cos(x)] = 1+sinx.cosx
proved