derive the equations of motion from y<sup>..</sup> = -g and x<sup>..</sup> = 0
then youll get x=170cos@ t and y = -gt<sup>2</sup>/2 + 170sin@ t
make t the subject in the x equation and sub that into the y equation. youll get a cartesion equation without the t. sub in x = 100, y = 1.5 and solve for @.
for this im assuming its fired from the origin.