In order to solve two dimensional problems it is necessary to break all vectors into their x and y components. Different dimensions do not 'talk' to each other. Thus one must use the equations of Motion once for the x-direction and once for the y-direction.
Scalar multiplication of vectors using vector components
Determining the magnitude of a vector using the Pythagorean theorem
Determining the magnitude of a vector using trigonometry
Determining the vertical vector component using trigonometry