1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Trig Quadrant Help

  1. Jul 13, 2012 #1
    1. The problem statement, all variables and given/known data

    Determine the following and state quadrant.


    2. Relevant equations

    I make this the 2nd quadrant.

    3. The attempt at a solution

    -cos(180 - θ)
    -cos ( 180 - (-65))
    = 0.423

    however i wasnt sure if it lied in the 4th quadrant
    -cos(360 - θ)
    -cos ( 360 - (-65))
    = 0.423

    Can anyone help me understand this PPPPUUUUURRRRRRLEASE. :confused:

    Thanks guys.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jul 13, 2012 #2


    User Avatar
    Homework Helper

    This will be an easy one to answer if you know how the angles move.

    Basically you start on the positive x-axis and travel in a circle in a counter-clockwise fashion. So at 10o you'll be in the 1st quadrant and very close to the x-axis. At 45o you're half way between the x-axis and y-axis in the 1st quadrant. At 90o you're now on the positive end of the y-axis. You continue to move counter-clockwise and now you've hit the 2nd quadrant.

    Negative angles however are defined as starting at the same point on the x-axis but instead you now move clockwise, so at -10o you're suddenly in the 4th quadrant.
  4. Jul 17, 2012 #3
    Sorry for the late response.

    Thank you for the reply all sorted now thanks to ya:)
  5. Jul 17, 2012 #4


    User Avatar
    Science Advisor

    So you have realized that -65° is in the fourth quadrant, not the second?
  6. Jul 17, 2012 #5
    Yes i got there in the end. Problem is im doing a self study course and the notes are horrific. Wish i had knuckled down when education was free.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook