Find the tangent of a point on a cubic bezier curve

Question

For a cubic Bézier curve, with the usual four points a, b, c and d,

for a given value t,

how to most elegantly find the tangent at

Answer 1

I found it too error-prone to use the supplied equations. Too easy to miss a subtle t or misplaced bracket.

By contrast, Wikipedia provides a much clearer, cleaner, derivative IMHO:

...which implements easily in code as:

3f * oneMinusT * oneMinusT * (p1 - p0)
+ 6f * t * oneMinusT * (p2 - p1)
+ 3f * t * t * (p3 - p2)

(assuming you have vector-minus configured in your language of choice; question isn't marked as ObjC specifically, and iOS now has several langs available)