`sin4A=4sinA*cos^3A-4cosA*sin^3A`

Prove that : sin 4A=4 sinA cos^3 A- 4 cosA sin^3 A .

sin4A = 4sin A cos ^ (3) A-4cos A sin ^ (3) A

sin(A-B)=sinA cos B-cosA sinB

If secA=5/4 , verify that (3sinA-4sin^3A)/(4cos^3A-3cosA)=(3tanA-tan^3A)/(1-3tan^2A)

sin4A=4cos^(3)A sin A-4sin^(3)A cos A

Prove that (sin3A+sinA)sinA+(cos3A-cosA)cosA=0

Prove that: (sin7A-2sin4A+sinA)/(cos7A-2cos4A+cosA)=tan4A

Prove that: (sin7A-2sin4A+sinA)/(cos7A-2cos4A+cosA)=tan4A

Prove that a) (sin3A + sinA)sinA+(cos3A-cosA) cosA=0 b) cos20^(@)cos40^(@)cos80^(@)=1/8 c) (sin8thetacostheta-sin6thetacos3theta)/(cos2thetacostheta-sin3thetasin4theta) = tan2theta

On simplifying (sin^3A+sin3A)/(sinA)+(cos^3A-cos3A)/(cosA) we get