- #1

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[tex]\sin^4 - \cos^4 = 1 - 2\cos^2[/tex]

i have tried approaching this identity by solving the RHS (right hand side) of the equation but this lead no where. however i am unsure on how to maniplulate the LHS of this equation because of the power of 4. would somebody please be able to give me a slight hint in which direction to head to prove this?

many thanks,

Pavadrin