The slope (i.e. derivative, gradient) of a parabola at any point is
dy
-- = 2x
dx

For example, the slope at x=1 is 2*1=2, while the slope at x=2 is 2*2=4.

To find the angle that you need to rotate, plug the slope into the inverse
tangent function (which is called "atan2" in POV-Ray).

-Nathan

mick wrote:
> 
> Help!
> 
> I have drawn a parabolic shape using the formula y = X^2
> 
> The parabola is composed of spheres scaled into ellipses with the longside
> in the y direction
> 
> I have been trying to rotate each ellipse so the the length is pointing in
> the direction of the parabola
> 
> I need to calculate the gradient at each point. I'm no mathmatician so
> Please help

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