So I'm trying to analyze the following contour map (visually) and point to the correct function that represents it. I'm not quite sure how to approach this at all, as everything I've tried gives me weird results without really seeing anything clear.
Would appreciate some help, thanks in advance!
The diagram is not symmetrical about the vertical axis, it can't be a contour plot of the two stated function involving $\cos(2x)$ which is an even function.
If $y=-2x$, then we have $\sin(2x)+\sin(y) = \sin(2x)+\sin(-2x)=0$, which is a constant.
If $y=-2x$, we have $\sin(2x)-\sin(y) = \sin(2x)-\sin(-2x) = 2\sin(2x)$ which is not a constant.
Hence the only possible candidate is $\sin(2x)+\sin(y)$.