A mathematician is verifying a table of trigonometric identities for the variable α\alphaα.
Using the compound angle identity for sin(A+B)\sin(A + B)sin(A+B), derive the identity for sin2α \sin 2\alpha\,sin2α in terms of sinα \sin \alpha\,sinα and cosα\cos \alphacosα.
Using the compound angle identity for cos(A+B)\cos(A + B)cos(A+B), derive the identity for cos2α \cos 2\alpha\,cos2α in terms of sinα \sin \alpha\,sinα and cosα\cos \alphacosα.
Hence, write cos2α \cos 2\alpha\,cos2α as an expression containing only the term cosα\cos \alphacosα.
Hence, write cos2α \cos 2\alpha\,cos2α as an expression containing only the term sinα\sin \alphasinα.
Utilize the addition formula for tan(A+B)\tan(A + B)tan(A+B) to find an expression for tan2α \tan 2\alpha\,tan2α in terms of tanα\tan \alphatanα.