Expert: Paul Klarreich - 10/1/2008

Question
Differentiate:  y = (1 + cos x) / (1 – cos x)

Answer
Questioner:   Marie
Category:  Calculus
Question:  Differentiate:  y = (1 + cos x) / (1 – cos x)
................................................
Hi, Marie,

y = (1 + cos x)
   -----------
   (1 – cos x)

Looks like quotient rule:

dy   ()() - ()()
-- = ------------
dx        ()^2

dy   (1 – cos x)(- sin x) - (1 + cos x)(sin x)
-- = -----------------------------------------
dx        (1 – cos x)^2

dy    - sin x + cos x sin x - sin x - cos x sin x
-- = --------------------------------------------
dx           (1 – cos x)^2

dy    - 2 sin x
-- = -----------------
dx    (1 – cos x)^2

Next time, tell me:
-- what you are studying (exactly, not just 'calculus')
-- what you already tried to do.
and I can help more.