Angle in Radians

[Deleted]

Hi,

I was wondering if anyone had a formula to find the angle contained between the y-axis (the x axis would be fine too) and a set of coordinates in radians.

e.g.
x=276
y=117

I always hated trigonometry and cant seem to remember the formula's.

A picture of what I mean:

[rademach]

Its probably easier to find the angle in degrees and just convert it into radians. Your angle is arctan(y/x). Multiply that by 2pi/180 to find the measurement of the angle from the positive x axis. Then simply add pi/4 to find the angle from the negative y axis.

edit: it sounds like you're asking for polar coordinates. Use the Pythagorean theorum to find the magnitude of the ray you're looking to measure. Your answer will be in the form (magnitude,direction)

[bohapjut]

i thought 0 was on the right side, with π on the left instead of 0 on bottom

[morbidjbyrd]

That pic makes no sense......it should have

0 radians on Right,
pi/2 radians on top
pi radians on left,
3/2*pi on bottom

Degree to radian,
Angle/180 = x*pi

ie, 90 degrees
90/180 = 1/2 * pi

Radian to degree
x pi *180 = angle

ie, 2 pi
2 pi * 180 = 360 degree

Edit: If you need to find the angle (x,y)
Simply create a triangle with the x or y axis and use arctan to find the angle,

ie,
Tan (theta) = y/x

arctan (theta) = arctan (y/x)

[Maharishi]

That graph is mind blowing, no one ever starts from the Y axis.

There is no explicit formula, here's how you'd do it (note i didn't bother relabeling the axis, x is 0 pi yadayada):

[Deleted]

Haha seems I confused some people unintentionally. The reason I needed this was for:

PlayerModel:SetRotation(rotationRadians)

The problem with this was that 0 radians is straight down (or (0, -1)) which is why I was starting at the negative Y axis. It wasn't until I looked at Maharishi's diagram that I realized that I should be adding pi/4 to the radians rather than subtracting (the main reason I was so stumped and thought I was missing something really important in the 1st place).

After sorting that it was easy, I just placed an offset if x < 0 (which btw I put as +pi/2 at first...damn brain farts)

In case anyone needs this in the future here is how it looks:

local radi = rad(atan(y/x)) + (3.14/2)

if x < 1 then
radi = radi + 3.14
end

Frame:SetRotation(radi)

Thank you all for the help, it was very much appreciated.

[Maharishi]

Did you already build the code and have it work? As someone else mentioned, the graph is incorrect as 360 degrees is 2pi, not 1pi, so in your case the offset should be pi/2 not pi/4, right?

[Deleted]

Did you already build the code and have it work? As someone else mentioned, the graph is incorrect as 360 degrees is 2pi, not 1pi, so in your case the offset should be pi/2 not pi/4, right?

Aha you are right, seems I fixed the "radi = radi + 3.14/2" part that I had in and forgot about everything else. I updated the code above.

[bohapjut]

fixed graph angles on picture for you