cos(θ) is the x-coordinate of the point P and, sin(θ) is the y-coordinate of the point P. This applet shows how the graphs of sin(θ) and cos(θ) follow directly from the definition of these functions.

However there's often more than one answer expected so be aware of this. Let's remind ourselves of what the sine graph looks like so that we can see how many solutions we should be expecting ...