12. Prove that:
sin^3+cos^3/
sin+ cos - sin cos =1
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Step-by-step explanation:
use the identity (a^3+b^3)= (a+b) (a^2+b^2-ab)
sin^3A+ cos^3A (sinA +cos ). + sinA.cosA (sinA+cosA)(sin^2+cos^2 -sinA.cosA)+ (sinA + cosA)+ sinA.cosA
or( sinA^2+cosA^2 -sinA.cosA) +sinA.cosA
1-sinA.cosA+sinA.cosA 1
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