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This question shows you are not familiar with the subject. My advice is that you should read your textbook/notes again. Work out few simple problems.And also, I'm confused about this.. is -tanx-tanx equal to -2tanx or -tan2x?
By the way -tan x -tan x = -2 tan x
I will answer your question, but I doubt you will understand every step clearly. First read the identities and know them clearly and then re read my post, you will understand the solution.
For the first equality, I have used the relation
For the second equality I have used