How to find an angle in range(0, 360) between 2 vectors? I know that the common approach in order to find an angle is to calculate the dot product between 2 vectors and then calculate arcus cos of it. But in this solution I can get an angle only in the range(0, 180) degrees. What would be the proper way to get an angle in range of (0, 360)?

I write the formula like I wrote in excel . (xa,ya,xb,yb put in the cells a2,b2,c2,d2).
angle(vector.a,vector.b)
=(180/pi())* abs(pi()/2*((1+sign(a2))* (1-sign(b2^2))-(1+sign(c2))* (1-sign(d2^2)))
+pi()/4*((2+sign(a2))*sign(b2)-(2+sign(c2))*sign(d2))
+sign(a2*b2)*atan((abs(a2)-abs(b2))/(abs(a2)+abs(b2)))
-sign(c2*d2)*atan((abs(c2)-abs(d2))/(abs(c2)+abs(d2))))
The formula is giving the angle of two vectors a and b from 0 to 360 degrees,
in left wise direction for any value of the vectors coordinates.
For xa=ya=0  and  or xb=yb=0 the result is undefined.
