Answer
$\frac{4}{3}$
Work Step by Step
Step 1. Using the given figures, we have $a=-\sqrt {5-4}=-1, b=-\sqrt {1-\frac{1}{16}}=-\frac{\sqrt {15}}{4}$
Step 2. $h(2\theta)=tan(2\theta)=\frac{2tan\theta}{1-tan^2\theta}=\frac{2(-2)}{1-(-2)^2}=\frac{4}{3}$