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Just a little trig help

  1. Mar 1, 2009 #1
    1. The problem statement, all variables and given/known data

    Well I'm following an example problem on this site:
    http://www.batesville.k12.in.us/physics/PhyNet/Mechanics/Circular Motion/banked_with_friction.htm
    I just need some help on the derivation math. I'll just host the image below.

    2. Relevant equations
    This is the problem equation:
    http://img105.imageshack.us/img105/3449/frictioneqn4.th.gif [Broken]

    On the last line when it goes from sines and cosines to tangants I can't follow what the person did.

    3. The attempt at a solution

    I'm assuming he used some type of trig Identity but I can't find one that is apt. I thinking it's a sum/difference trig identity but it just doesn't help. What could he be doing?

    Any help at all is GREATLY apperciated!

    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Mar 1, 2009 #2


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    Homework Helper

    Multiply top and bottom by 1/cosθ
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