Who is asking: Parent
Level: Secondary

We have spent hours trying to solve the following identity without success. Can you give us some hints as to how it is done?
1 + tan(x) tan(2x) = tan(2x) cot(x) -1
Thank you very much!



Hi Ron,

I used the expression for the tangent of 2x and manipulated the left side to get

For the right side, write the cotangent as 1 over the tangent and expand the tangent of 2x as I did above. Put the two terms over a common denominator and you should get the same expression that I have above.



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