I don't know why you would need the correlation coefficient. Have you started by graphing the two lines? Do you know that the gradient of a line can be found by , where is the angle measured in the anticlockwise direction of the positive x-axis? If you have the gradients of the lines (which you should be able to get quite easily), you can evaluate the angles made with the x-axis, and with a diagram you should then be able to use basic geometry to evaluate the angle between your two lines.
You always need to TRY some things BEFORE asking for help, and you should post WHAT you have done so that we know WHERE you are stuck and need the specific help.