Find launch angle

Mar 2018
I found this question in a textbook and the calculation was not shown. The launch velocity is 6 times the velocity at maximum height, find launch angle. Can someone help me by showing me calculations.
Jul 2009
You need to work out the ratios of the velocities. You have enough information to work out what is the ratio of the horizontal velocity component compared to the total velocity at launch. Using this and basic trigonometry, it is possible to arrive at the launch angle even though you do not know what the actual velocities are. Hint: When the object reaches maximum height then the magnitude of the horizontal velocity is equal to the magnitude of the total velocity.