Python Forum

So, i've been trying to find this out for such a long time.
So say I have three points A, B, C. Each with X and Y values.
ax = 1
ay = 5
bx = 1
by = 2
cx = 5
cy = 1
which looks something like this on a graph:
5 | A . . . .
4 | . . . . .
3 | . . . . .
2 | B . . . .
1 | . . . . C
0 * - - - - -
* 0 1 2 3 4 5
and i want to find the angle between A & C as if it were around circle B
also, 0-360

what have you tried? We are glad to help, but we won't do your [home]work.
Post your code in python tags, any errors in error tags, ask specific questions.

The function math.atan2() may help you solve this.

here is what i have so far:

import math
p1x = 0
p1y = 5
p2x = 0
p2y = 0
p3x = 5
p3y = 0
angle1 = (math.atan2(p3y - p1y, p3x - p1x) - math.atan2(p2y - p1y, p2x - p1x))
print(angle1)

based on something i found online, but not sure if it is correct, also it just gives
0.785(irrational) and i want a 0-360 number.
edit: i changed it to deg with math.degrees,
but still doesn't work to my full intentions
and gives me 45 deg when its 90 deg

It is almost correct. The order of the points matters

import math

def angle3pt(a, b, c):
    """Counterclockwise angle in degrees by turning from a to c around b
        Returns a float between 0.0 and 360.0"""
    ang = math.degrees(
        math.atan2(c[1]-b[1], c[0]-b[0]) - math.atan2(a[1]-b[1], a[0]-b[0]))
    return ang + 360 if ang < 0 else ang

print(angle3pt((5, 0), (0, 0), (0, 5)))

Output:
90.0

This function will not throw an error if a==b or c==b because math.atan2(0,0) returns 0.0. It would probably be a good idea to add this in the function, something like

    if b in (a, c):
        raise ValueError("Undefined angle, two identical points", (a, b, c))

qrani

buran

Gribouillis

qrani

Gribouillis