I suppose this is also related to thrust vectors.
I have a Y pipe with two exit nozzles. These exit nozzles are angled 43.75 degrees from the vertical and are at a radius of .1968m from the vertical. These nozzles have a deflector that can move from 0 degrees (fully open), to 90 degrees...
The scalar product (or dot product) of two vectors is a scalar that is proportional to the length of the projection of the first vector onto the second vector. An example would be a vector A which is 2 units long on the positive x-axis and a vector B which is at a 45 degree angle to the x-axis...