Chapter 7 - 7.5 - Multiple-Angle and Product-to-Sum Formulas - 7.5 Exercises - Page 549: 72

$θ\approx23.847°$

$r=\frac{1}{32}v_0^2~sin~2θ$ $v_0=75~ft/s$ and $r=130~ft$ $130=\frac{1}{32}(75)^2~sin~2θ$ $130=\frac{5625}{32}~sin~2θ$ $\frac{130\times32}{5625}=sin~2θ$ $sin~2θ=0.7395555...$ $2θ=arcsin(0.7395555...)$ $θ=\frac{arcsin(0.7395555...)}{2}$ $θ\approx23.847°$