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

Current in circuit (trig problem)

  1. Feb 25, 2007 #1
    Hey this is my first post... been really stuck on this particular question from a paper:

    In a particular circuit the current, I amperes, is given by:

    I=4sinθ - 3cosθ θ>0

    where θ is an angle related to the voltage.

    Given that I=R x sin(θ-a), where R>0 and 0<=a<360degrees,

    a) find the value of R, and the value of a to 1 decimal place.
    b) Hence solve the equation 4sinθ - 3cosθ = 3 to find the values of θ between 0 and 360degrees.
    c) Write down the greatest value for I.
    d) Find the value of θ between 0 and 360degrees at which the greatest value of I occurs.

    I think if someone could show me the steps to answering part a) I could be able to do the rest myself.
  2. jcsd
  3. Feb 25, 2007 #2


    User Avatar
    Science Advisor

    [itex]Rsin(\theta- a)= Rsin(\theta)cos(a)- Rcos(\theta)sin(a)[/itex]

    Compare that with I.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook