As there is no acceleration in horizontal direction the velocity component will remain same as VcosƟ and at highest point vertical component will be zero.
So total velocity at top will be VcosƟ
Kinetic energy at the highest point will be= ½ m( VcosƟ)2
Initial kinetic energy will be =1/2mV2
At highest point
kE at highest =3/4 kE initial
1/2 m( VcosƟ)2 =1/2mV2 *3/4 cosƟ=(3) 12/2
Ɵ=30 degree