Question

(cos 3 theta + sin 3 theta /cos theta +sin theta) + (cos 3 theta -sin 3 theta / cos thetha -sin thetha)

Answer 1

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