width of the trace and printed circuit board

1. Measure it?? Or do you mean to ask how you can determine what width trace you should use for a particular application? If it's the latter, it depends on several things: do you need a particular impedance? How much current will it carry? What temperature rise can you tolerate? How much voltage drop can you stand? What is the PC process you are using capable of?
2. Is K the same as k? If not, what is it? What is k? What are D and H? What does the formula claim to determine?

You may well find answers to your questions with a Google search about printed circuit trace width. For example, this was one of the early hits of such a search:

Cheers, Tom

If what you are considering is how wide to make digital traces, you need to also take into account the ability of the drivers to drive them. The impedance of the trace and hence the current required by the driver is a function of the trace geometry: width versus height above the reference plane.

As a rule of thumb and unless there are other considerations, I try to keep the digital traces on the order of 75 Ohms though I don't worry too much about it. I chose 75 Ohms mostly on the advice of another engineer who's opinion and abilities I respect. When I asked him to review a PCB layout for me, he commented that my 50 Ohms traces might be a little low for some drivers to handle, though most modern stuff could, and I might want to consider going a bit higher. Based on the standard core thickness used by the PCB vendor I use I typically keep my digital traces at .008", which gives me an appropriate impedance and is still reliably producible.

The capabilities of the PCB vendor are another factor to keep in mind, as is the cost of your design choices.

I normally use a magnifier with a graticule...