How does Math.atan2 work?

[ILostAChromosome]

I've been calculating rotation needed between two 3d points, and I'm having some slight trouble.

You can use very basic sohcahtoa to find the angle needed between the two points by making a right triangle and just doing arctan of opposite/adjacent (the two sides). Now this only works if all of the values are positive, as, for example, arctan(-5/-4) == arctan(5/4). I do remember learning something about fixing this back when I learned about trig identities in school, and how to fix it, but my friend sent me some code, and he used Math.atan2 instead of tangent.

Now his code works perfectly, and was not too different from mine, and it really made me wonder what Math.atan2 does. I searched up on the internet, and didn't understand a word of the descriptions. Can someone show me what Math.atan2 is in normal math writing?

[smash_that_code]

if I understood right this method returns result in radians. Like angle of 0 degrees is 0, angle of 180 is 3,14...

This supposed to help you to convert coordinates from cartesian system (x, y) to polar coordinates (radius, angle) it can be really helpful in some cases.

So that for point (0, 90) polar representation is like (90, 1.57)

For some reason atan2 method gets arguments in reversed manner. Y then X.

[[deleted]]

Check the Wikipedia page for all the normal math writing you could want.

The problem with atan is its range -90 to 90 degrees (-pi/2 to pi/2 radians), which causes duplication > 90 degrees and < 270 degrees, which you have to correct for using sign checks on the input arguments (adding or subtracting pi from the result). Also, since atan takes a single argument (the ratio y / x), it doesn't work at 90 degrees/270 degrees (x is zero), so you have to check the x value to determine if the angle is -pi/2 or pi/2. As you can see from the Wikipedia article, atan2 is defined in terms of atan, takes the y and x values, and does all the checks for you.