[tex]\text{Aplicam formula:} \boxed{a^3+b^3=(a+b)(a^2-ab+b^2)}\\
\sin^3x+\cos^3x=(\sin x+\cos x)(\sin^2x-\sin x\cdot \cos x+\cos^2x).\\
\text{Stiind ca:}\boxed{\sin^2x+cos^2x=1},obtinem:\\
\sin^3x+\cos^3x=(\sin x+\cos x)(1-\sin x\cdot \cos x),c.c.t.d[/tex]