HW 1 due 15 Jan CLARIFICATION

student asks:

In problem four of the homework due Jan 15, when you say "find the
magnitude of and angle of a + b," do you mean the angle of a + b
relative to b, like in bullet number two?

Ok, that is not quite clear enough ...

For the last two cases in that problem, I mean the angle with respect to the x axis.

For example, if

\vec{c}=\vec{a}+\vec{b}

then the angle is

\tan^{-1}{\left(c_y/c_x\right)}