Maxscript: This demonstrates how to calculate the length of an arc when the radius and two points are known

Length Of Arc Between Two Points & Radius | .ms

-- length = 12.6
-- radius = 10
-- angle 72

-- get arc length
arcLength = 2*pi*10*(72.0/360.0)


-- get arc angle
arcAngle = 360.0 * (2.0/10.0)

-- 2*10*(72.0/360.0)
-- 360 * (2.0/10.0)

-- How do I calculate arc angle between two points on a circle?
-- cos-1 ((x1x2 + y1y2 + z1z2) / r2)

-- startPoint = [3.0,5.196,0.0]
-- endPoint = [0.0,12.0,0.0]
startPoint = [6.749,8.043,0]
endPoint = [0.0,10.5,0.0]
origin = [0,0,0]
radius = 10.5

print "Length of arc between two points with known radius"
x = startPoint.x * endPoint.x 
y = startPoint.y * endPoint.y 
z = startPoint.z * endPoint.z 
acos( (x+y+z)/(pow radius 2) )