Show that a nonzero polynomial function y = (x) cannot satisfy the equation y'= y. Use this to prove that neither (x) = sin x

Show that a nonzero polynomial function y = ƒ(x) cannot satisfy the equation y'= −y. Use this to prove that neither ƒ(x) = sin x nor ƒ(x) = cos x is a polynomial. Can you think of another way to reach this conclusion by considering limits as x→∞?