1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    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!

Solving a Trig Problem - is this iterative only?

  1. Mar 18, 2008 #1
    1. The problem statement, all variables and given/known data

    Find when this is "0" for the first time:

    [tex] q(t) = e^{-20t} (5cos(40t) + \frac{5} {2} sin(40t)) [/tex]


    2. Relevant equations



    3. The attempt at a solution

    [tex] 0 = e^{-20t} (5cos(40t) + \frac{5} {2}sin(40t)) [/tex]

    [tex] 0 = (5cos(40t) + \frac{5} {2}sin(40t)) [/tex]

    [tex] cos(40t) = -\frac{1} {2}sin(40t)) [/tex]


    Is the best way to solve this perform interations?

    Thanks
    Sparky
     
    Last edited: Mar 18, 2008
  2. jcsd
  3. Mar 18, 2008 #2
    Iterations on what? You've basically solved it. Make that into [itex]tan(40t) = -2[/itex] and apply arctan. If you don't want a negative number in the argument, you can use the fact that arctan is an odd function.
     
  4. Mar 18, 2008 #3
    Thanks Kreizhn,

    I'm now embarrassed.

    this was not seeing the forest for the trees.

    I was about to open Excel and try different values of t until I got it to work out.

    Thanks
    Sparky
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Solving a Trig Problem - is this iterative only?
  1. Solve the trig (Replies: 3)

Loading...