I would suggest that you first draw a diagram.

The vector has a component of length in the x direction, and a component of length in the y direction. The length of the hypotenuse of the triangle (which is the length of the vector) is given by .

Now, assign the angle between the vector and the positive x axis the value . Can you try to visualize what I described?

You should then be able to determine and .

Does this make sense?