Answer
$\approx$ 106°
Work Step by Step
$\frac{longer diagonal}{2}$= $\frac{shorter diagonal}{2}$ $\times$ tan $\frac{obtuse angle}{2}$
8 in. = 6 in. $\times$ tan $\frac{obtuse angle}{2}$
tan $\frac{obtuse angle}{2}$ = $\frac{4}{3}$
$\frac{obtuse angle}{2}$ $\approx$ 53°
obtuse angle $\approx$ 106°