Adding velocities ( ? ) to get Speed

[King_Cool]

Hi
Im not sure im using the correct lingo here.
Feel free to correct me.

...
I have a moving Object.
I am able to accurately predict, what i call, the Objects X and Y velocity at any given time.
However, what i need to be able to predict is the Objects Speed at any given time ( see illustration below ).


...
How can i get the Absolute Speed from X and Y vel?

...Or even better:
I recently was intruduced to a site from someone on this forum
http://www.wolframalpha.com/input/?i=3*X+%3D+75

It appears to be quite usefull if one knows how to use it.
Can i solve this problem by using this site?
If so how?
( i realize this might be too simple a question for the site to be usefull )

[MuddyMole]

Suppose you redraw your diagram to look like this:

Does that look familiar?

[King_Cool]

Oh darn!
Yes that does look familiar, thanks for pointing that out :P
I was thinking Pythagoras but couldnt see it, because of my way of thinking about it i guess.