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1. I don't know where to start.

Sorry, I'm just really stupid today (if not every day).
2. (Original post by StarvingAutist)
I don't know where to start.

Sorry, I'm just really stupid today (if not every day).

look at Q96 how to do tan4θ and adapt it
3. you know by De Moivre that:

1) Expand the left side (as a binomial expansion)

you get, after sorting into real and imaginary parts:

these correspond to the real/imaginary parts of the right-hand-side.

Divide the imaginary part by the real part (and you have sin(3x)/cos(3x) = tan(3x) (at least on the lhs)

then divide the top and bottom of the fraction you get by

(this doesn`t alter it , if you times top and bottom by same thing)
4. (Original post by TeeEm)

look at Q96 how to do tan4θ and adapt it
Ah I see, thanks

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