1 is an obvious solution, and a graph sketch confirms it's the only one, since sqrt(1 - x^2) would have a upper semicircular graph, and exponentiating preserves order, so the graph shape would still be "up then down", enough to ensure 1 is the only solution. Though and algebraic approach escapes me, so ... time to watch.
I want to point out that critical points are not just were the function has a zero slope but rather where the slope is also undefined and that can happen at points of discontinuity, a sharp cusp or a vertical tangent.