Answer
See work.
Work Step by Step
The velocity vector at maximum height is horizontal, with magnitude $v_ocos \theta_o$. The vertical velocity component is zero, and the horizontal component is the same as at the time of launch.
The speed at maximum height is $v_ocos \theta_o$. The vertical velocity component is zero, and the horizontal component is the same as at the time of launch.
The acceleration vector at maximum height is vertically downward, with magnitude $9.80 m/s^2$. The vertical acceleration is constant.
