hello from mrbilldoesmath!
answer: x^2 + y^2 = 1024
the equation of a circle with center (h,k) and radius "r" is
(x-h)^2 + (y-k)^2 = r^2.
in our case
(x-0)^2 + (y-0) ^2 = 32^2 = 1024
can i see the following ?
First of all, we can just ignore A, it has no effect but to vertically stretch our cosine.
If it was only , the function would be invertible as long as it's confined between and . Now, the argument of our cosine is not but . It means that it won't stop at , but at .
Another way to think about it, "what should i replace x with so I get inside the cosine?"