# How to use Weibull distribution when it comes to wind?

## Homework Statement:

I'm asked to find out how many hours of the year that the wind is between 4,5 m/s and 5,5 m/s.

## Relevant Equations:

Weibull formula
I know that I'm supposed to use Weibull, but why does my teacher take the middle value, 5 m/s? Should one not integrate the formula and the use 4,5 and 5,5 as limits? This is what he has done:

He then writes: makes a guess of an interval of 1 m/s and get:

To be honest, I really don't understand how to use Weibull distribution, and it would be great if someone could explain. I tried finding some websites, but I don't understand. How do I find the probability for one specific wind speed, or find the probability for an interval like this problem I posted?