Video shows cortana in action on windows 10

Microsoft didn't mentioned that there will be cortana at the preview of windows 10. But rumors claimed that they are working on it as Microsoft wants to make a continuous experience for users it was very much plausible. 

The new video posted on YouTube shows the cortana in action. It is still in beta and is very limited in function. It can be triggered from start menu and works similarly as it works in windows phones.