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

Please help! Trigonometry question.

  1. Oct 27, 2007 #1
    Why is cos(arctan x) = 1 / root(1+x^2)

    and sin(arctan x) = x / root(1+x^2)?

    I would greatly appreciate help. I'm studying for physics and this came up in one of the solutions. Thank you.
     
  2. jcsd
  3. Oct 27, 2007 #2
    Think of a right triangle with sides 1 and x. Now try to imagine the values of:
    - The hypotenuse, and
    - The sin, cos and tan of the angle next to the "1" side.
     
  4. Oct 27, 2007 #3

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Well, you could show this algebraically, however:

    What is arctan(x)? arctan(x) is that angle whose tan-value is x.

    Now, writing x=x/1, remember that tan can be thought of as the ratio between two of the sides in a right-angled triangle.

    Identify which sides these are, and see if you can deduce the results for yourself.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Please help! Trigonometry question.
  1. Trigonometry help (Replies: 7)

  2. Trigonometry Help (Replies: 7)

Loading...