Answers for "how to find perpendicular slope"

how to write a perpendicular equation with given points

Sorry that you have to do math as will.

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)