Hey all! My calculus book goes through the proof/derivation of Kepler's first Law of planetary motion and I got to the part where the the indefinite integral of a vector valued function and got the answer plus the constant function. When the constant function was depicted in a diagram it was shown along the x-axis instead of along the vector of the answer. I guess the question I am asking is how to determine what direction the constant function points after computing an indefinite integral. For example: If [itex]\int[/itex]u' dt where u is a vector valued function you get u + c where c is a constant function. How do you determine the direction that c points?