1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Precalculus: proving trigonometric identity

  1. Mar 9, 2010 #1
    1. The problem statement, all variables and given/known data

    prove that: tan(1+cos(x))^2 = 1-cos(x)

    2. Relevant equations

    trig identities, like the pythagorean, sum/difference, double/half angle identities, power reducing identities, etc...

    3. The attempt at a solution

    i'm not sure where to start; i tried using the pythagorean identity where 1+tan(X)^2 = sec(x)^2, but couldn't get anywhere after that :\

    then i used my calculator and made X a random number. i typed in the left side expression, and pressed enter. i then typed in the right hand expression, and pressed enter. the two values were different. what did i do wrong?
    i'm not really sure anymore that its even possible to prove the above...
     
  2. jcsd
  3. Mar 9, 2010 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    You're right. It's not an identity. Just put x=0. Then you don't even need a calculator. Must be some mistake here.
     
  4. Mar 10, 2010 #3
    If I'm write you want to write [tex]tan(1 + cos x)^2[/tex] = 1 - cos(x). I think it is not possible to prove because if cos (x) is zero then [tex]{tan}^2{1}[/tex] is not equal to 1. Even if the equation is [tex]tan(1 + {cos}^2{x})[/tex] then also you can't prove it. I think, the problem is not to prove but to solve.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook