Find theta, 0 < theta < 2pi, if tan theta= 0.66

Find theta, 0 < (or equal to) theta < (or equal to) 360 if cos theta= -0.89

Am I over-thinking these questions or does it actually have an extensive answer? To me, my guess is for 1, to do .66 tan-1 and for 2, to do -0.89 cos-1, but that seems to simple.