finding launch angel from velocities

I'm having troubling finding a launch angel from a set of given velocities.

v=2[itex]\hat{i}[/itex], 4[itex]\hat{j}[/itex] at t=0

v=2[itex]\hat{i}[/itex], 2[itex]\hat{j}[/itex] at t=1

v=2[itex]\hat{i}[/itex] at t=2

v=2[itex]\hat{i}[/itex], -2[itex]\hat{j}[/itex] at t=3

the g=-2 on this planet