Help me with maths on my program!

Hello, i am in need of help with doing some calculations on my program. I am not really in all the math functions but i want to learn the way how can i calculate the right x and y speed for ball to go on correct angle. like if ball's y speed was 1 it would go just up. (0°) Actually i want the ball go in the direction of certain position to mouse's position. Can anyone help me with this, i found much similar stuff to this but not well explained. Heres example: YouTube - Little Java game also theres source for the code used but its commented in norway and the maker havent responsed yet. Can you guys please help me with this?