php - Describe relative angles between points (like driving directions) -

I have a list of digits with x, y coordinates, I sqrt (pove ($ x2 - $ x1 , 2) + How can I get the distance between points ($ y2 - $ y1, 2)) and Atan2 (y1 - y2, x1 - x2) .

How do I calculate the relative angle between points (left, right, right)? So, if I'm at 1 point, then what is the relative direction for point 2, then 2 to 3, 3 to 4 etc. ...

Thanks for any help!

call

If it is between π / 2 and 3π / 2, So this is straight.
If this is less than 3π / 2 or less than -3π / 2, this is a left turn.
If it is between -i / 2 and π / 2, then this is a perfect turn.

Here's a diagram:

 {3π / 2} ------- {π / 2} ------- {π / 4} | + ----- [+ y] ----- + | | | | | | | | | {Π} [-x] [0,0] [+ x] {0} | | | | | | | | | + ----- [-y] ----- + | {-3π / 2} ------- {- π / 2} ------ {- π / 4}