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: Verifying identity

  1. Nov 3, 2008 #1
    1. The problem statement, all variables and given/known data
  2. jcsd
  3. Nov 4, 2008 #2
    On the left hand side of the equation, you have sinX and on the right sinx.

    Is this capitalisation deliberate, or accidental.

    Assuming it's accidental, your first step would be to divide both sides by sinx.

    This gives

    1 - 2cos^2x + cos^4x = sin^4x.

    Can you do anything with that?

    Clue: Can the left hand side be factorised??
    Last edited: Nov 4, 2008
  4. Nov 4, 2008 #3


    Staff: Mentor

    Assuming that you need to prove that this is an identity, you can work with one side to show that it is equal to the other side, or work with each side separately to get to expressions that are identical.

    The left side is sin(x) (1 - cos^2(x))^2 [Parentheses would be very helpful in your original equation.]
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook