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!

It says convert (-1, pi/8 ) from polar to rectangular coordinate?

  1. Oct 2, 2011 #1
    How do you find these on the unit circle: 5pi/2 ? howabout pi/8 ? Converting from polar to rectangular?
    It says convert (-1, pi/8 ) from polar to rectangular coordinate? But there is no pi/8 on the unit circle?
    If the'yre on the unit circle just use x=rcosθ and y=rcosθ
    another example is for (1, 5pi/2) That doesn't seem to be on the unit circle either. So how can we do these then?
     
  2. jcsd
  3. Oct 2, 2011 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    -1 is your r and pi/8 is your theta. Like you said use x=rcosθ and y=rcosθ.
     
  4. Oct 2, 2011 #3
    YOU CAN'T
    it won't work unless they're on the unit circle
     
  5. Oct 2, 2011 #4

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    "polar coordinates" means the ordered pair is (r,theta). You want to convert that to (x,y). As long as |r|=1 it is on the unit circle.
     
  6. Oct 2, 2011 #5
    OK how, you keep saying you can do it, so please do, because that's what I'm asking. do it do it do it lol please haha

    p.s. the 5pi/2 that's just where pi/2 is, but the pi/8 WHERE is that?
     
  7. Oct 2, 2011 #6

    NascentOxygen

    User Avatar

    Staff: Mentor

    Last edited by a moderator: Apr 26, 2017
  8. Oct 2, 2011 #7

    eumyang

    User Avatar
    Homework Helper

    Are you saying that since π/8 is not one of the special angles (those related to 30°, 45°, and 60°), the angle is not "on the unit circle"? If that is the case, so what? Either use a calculator to evaluate the necessary trig functions of π/8, or use a trig identity.

    For example, if the point is (1, 105°), then in rectangular coordinates it's (cos 105°, sin 105°). Use a calculator and you get (-0.259, 0.966). Or use the fact that 105° = 60° + 45° and evaluate cos (60° + 45°) and sin (60° + 45°). That's it!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: It says convert (-1, pi/8 ) from polar to rectangular coordinate?
Loading...