Answer
$F = 577.168~cos~\theta$
When we graph this function, we can see that $F= 400~lb$ when $\theta \approx 46^{\circ}$
Work Step by Step
$F = \frac{0.6~W~sin(\theta+90)}{sin~12}$
$F = \frac{0.6~(200)~sin(\theta+90)}{sin~12}$
$F = 577.168~sin(\theta+90)$
$F = 577.168~cos~\theta$
When we graph this function, we can see that $F= 400~lb$ when $\theta \approx 46^{\circ}$