LaTeX-tikz drawing perpendicular line

[binbagsss]

I copied and pasted some code from another thread on this forum, and it has worked, however I am unsure how to change the length of the line. On the attached image, the line is the one labelled H(X,T). I want the line to be perpendicular to the plane- to pass through the blue node labelled (dfd) and a point of F(X,T), as it does. But I do not want it to go below dfd as it does at the moment.

This is the code I used:

\node

at (4.1,2.5) {H(X,T)};
\coordinate (C) at (7,3);
\coordinate (O) at (5.4,2.3);
\node at (5.4,2.3){dfd};
\tkzDefLine[orthogonal=through C](C,O);
\tkzDrawLine[,add = .6 and 0.02,color=black](O,tkzPointResult);

and changing the first parameter- the 0.6 shortens it from the other end , so e.g 0.4 was to short for it to intersect F(X,T), and I'm not sure what the other parameter does, I have changed it but have not noticed any difference. It is the length of the line from the other end that I want to control.

(On another note, how do I turn this into an arrow, when I tried `\tkzDrawLine[<->,add = .6 and 0.02,color=black](O,tkzPointResult)` it produced an error.

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[NateD]

Any help would be greatly appreciated.You can use the 'shorten' option in the \tkzDrawLine command to control the length of the line. For example, the following code will draw a line from dfd to F(X,T) with a length of 2cm:\node at (5.4,2.3){dfd};\tkzDefLine[orthogonal=through C](C,O);\tkzDrawLine[shorten >=2cm,color=black](O,tkzPointResult);To draw an arrow, use the '->' option instead of the '<->' option. For example:\tkzDrawLine[shorten >=2cm,->,color=black](O,tkzPointResult);