Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Trig related problem

  1. Aug 28, 2006 #1
    I'm trying to solve a physics problem with some trig in it. I'm looking at a solution but I'm not understanding where it gets from one step to another.

    I understand it up to this point:

    19.6m + 800m * cos(Z)^2 = 2,000m * sqr(1 - cos(Z)^2) * cos(Z)

    But I don't understand how they get from that to:

    384m^2 + 31,360m^2 * cos(Z)^2 + 640,000m^2 * cos(Z)^4 =
    4,000,000m^2 * cos(Z)^2 - 4,000,000m^2 * cos(Z)^4

    Is this some kind of crazy trig trick that I don't know about?
  2. jcsd
  3. Aug 28, 2006 #2

    Raise both sides of the equation to the second power and here you are (approximately, should have been 384.16m^2).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook