dcsimg
A Flash Developer Resource Site

Results 1 to 2 of 2

Thread: unit circle

  1. #1
    Junior Member
    Join Date
    Oct 2004
    Location
    rhode island
    Posts
    2

    unit circle

    I took trigonometry in 1983, so bear with any mistakes or mistatements below.

    When working with radians, I am assuming Flash is using the unit circle with a radius of one. Correct?

    If so, is 0 or 2(Math.PI) located due East or due North on the circle?

    Also, when considering degrees, where is 0 or 360 degrees located? It appears that this answer is due North. Correct?

    Thanks in advance.

  2. #2
    Junior Member
    Join Date
    Jul 2003
    Location
    London, UK
    Posts
    18
    Hi eugene,

    In mathematics, 3 o'clock is usually considered to be the natural baseline (0 degrees, 0 radians) and positive angles are measured counter-clockwise.

    So,
    Code:
     3 o'clock:   0 degrees =      0 radians
    12 o'clock:  90 degrees =   pi/2 radians
     9 o'clock: 180 degrees =     pi radians
     6 o'clock: 270 degrees = 3*pi/2 radians
    But, in Flash (and every other computer language that I can think of) positive angles are measured clockwise.

    So, if we CHOOSE the baseline to be 3 o'clock then we get
    Code:
     3 o'clock:   0 degrees =      0 radians
     6 o'clock:  90 degrees =   pi/2 radians
     9 o'clock: 180 degrees =     pi radians
    12 o'clock: 270 degrees = 3*pi/2 radians
    But, in the end, choosing a baseline is often irrelevant. If you want to rotate an object in flash, it is usually 'from it's current position', hence you only need to know by how much and in which direction.

    A positive rotation will be clockwise.
    A negative rotation will be counter-clockwise.

    Hope that helps.
    Paul

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  




Click Here to Expand Forum to Full Width

HTML5 Development Center