draw perpendicular line from the point of curve rhinoscriptsyntax
curve = rs.GetObject()
points = rs.GetObjects()
length = 50
for point in points:
pt = rs.coerce3dpoint(point)
param = rs.CurveClosestPoint(curve, pt)
normal = rs.CurveNormal(curve)
tangent = rs.CurveTangent(curve, param)
curveNormal = rs.VectorCrossProduct(normal, tangent)
rs.AddLine(pt, pt - curveNormal * length)