The kinetic energy of the ball at the highest point is as follows:the expression for kinetic energy is \\\\(KE=\\frac{1}{2} mv^2\\\\).So, the kinetic energy at the highest point is,\\\\(KE_h=\\dfrac{1}{2} m(v\\cos(45^\\circ))^2\\\\)\\\\(KE_h=\\dfrac{1}{2} m(v^2)(\\cos(45^\\circ))^2\\\\)\\\\(KE_h=E(\\cos(45^\\circ))^2\\\\)\\\\(KE_h=\\dfrac{E}{2}\\\\)so, at the highest point the kinetic energy is \\\\(\\dfrac{E}{2}\\\\).