1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Simplify trigno expression

  1. Apr 6, 2010 #1
    1. The problem statement, all variables and given/known data

    cos(2 * arcsin(2x))

    Use a triangle to simplify each expression. Where application, state the range of x's for which the simplification holds.

    2. Relevant equations

    cos(2t) = cos^2(t) - sin^2(t) = 1-2sin^2(t) = 2cos^2(t) - 1

    3. The attempt at a solution

    My attempt was the following


    let arcsin(2x) = delta (or t)
    so cos(2t) = double angle formula

    cos2(t) = 1-2sin^2(t)
    replace t, and by definition sin(arcsinx) = x
    so i think i got 1-2*(2x)^2 = 1-8x^2

    please verify for me

    thank you
  2. jcsd
  3. Apr 6, 2010 #2


    Staff: Mentor

    That's what I get.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook