# [metapost] Re: tangent

Boguslaw Jackowski B_Jackowski at GUST.org.pl
Mon Jan 17 18:57:04 CET 2005

```HP> Do you have any idea how to do a tangent to path p from point z.
[...]
HP> I meant general curve.

This foretells troubles:

1. The solution need not to be unique; but this problem can be (iteratively
or recursively ;-) overcome.
2. What about singular points, such as the point 1/2 of p, where
p=(0,0) .. controls (1,1) and (0,1) .. (1,0) ? You should rather
accept the path going through z and such a peak, although the
path direction is singular there, namely: (0,0).

HP> I found solution using loop to determine right point, where tangent
HP> and curve have same direction. But I do not believe it is the
HP> simpliest solution.

Could you present your solution?

-- Jacko

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Bogus\l{}aw Jackowski: B_Jackowski at GUST.ORG.PL
----------------------------------------------------------------
Hofstadter's Law: It always takes longer than you expect, even
when you take into account Hofstadter's Law.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

```