SOLUTION: Prove the identity. 5tan(3x) = (15tan(x) − 5tan^3(x))/ (1 − 3tan^2(x))

Question 1157401: Prove the identity.
5tan(3x) = (15tan(x) − 5tan^3(x))/ (1 − 3tan^2(x))
Answer by Edwin McCravy(20054) (Show Source): You can put this solution on YOUR website!



We will work only with the left side.  We will use this formulas:

                

               and its corollary:

                




Distribute the 5 to remove parentheses on the top and
multiply tangents on the bottom:





Distribute to remove the parentheses:



Combine terms:



Edwin

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