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# How would you show that 1/ (1 + cos x) = tan (x/2) +c watch

1. I am so so so confused
2. (Original post by TeeEm)
cos2x = 2cos2x - 1
cosx = 2cos2(x/2) - 1
Then what
3. (Original post by APersonYo)
Then what
Susbtitute for using the identity TeeEm gave you. Please post all your working if you get stuck.
4. (Original post by notnek)
Susbtitute for using the identity TeeEm gave you. Please post all your working if you get stuck.
I usually post my working. But I am so stuck on this question I have no working
5. (Original post by APersonYo)
I usually post my working. But I am so stuck on this question I have no working
TeeEm showed you this:

cosx = 2cos2(x/2) - 1

So change the cos(x) in 1/(1+cos(x)) using the above identity. Try this and please post what you get if you get stuck.

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