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1. ## 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?

2. 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

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