Monday, July 1, 2019

mathematics - How does atan2 work when getting angle of a vector?


I know that atan2 gives me the absolute angle of any vector. But it doesn't give a value from 0 to 360 degrees. Instead, it gives a value (if I'm not mistaken), between 0 and 180, or between 0 and -180. For example, instead of giving angle 270, it will say -90.


This is a little confusing for me. Let me try to describe how I think this works, and please tell me if I'm correct. Actually, I'll draw it.



enter image description here


Is this correct? I'm having a little trouble understanding this. Thanks



Answer



From the Wikipedia page:


Details of atan2 implementation


It is returning the shortest angle of rotation from the positive x direction to the point, where a positive angle indicates the counter-clockwise direction. Therefore it makes sense that it would only return values between 0 and 180, since anything greater than 180 can be 'better' approached by a smaller angle in the opposite direction.


Returning -90 instead of 270 also makes sense now, since moving 90 degrees clockwise is less than moving 270 degrees counter-clockwise to reach the same point. This also suggests that your interpretation has mixed up the positive and negative 90 degree directions but is otherwise fine.


No comments:

Post a Comment

Simple past, Present perfect Past perfect

Can you tell me which form of the following sentences is the correct one please? Imagine two friends discussing the gym... I was in a good s...