Appendix A - A.5 - The Quadratic Formula and Square Root Properties - Exercises - Page 555: 38

$b = 8$

We can find the value of $b$: $c^2 = a^2+b^2$ $b^2 = c^2-a^2$ $b^2 = (10)^2+(6)^2$ $b^2 = 100-36$ $b^2 = 64$ $b = \pm \sqrt{64}$ $b = -\sqrt{64}~~$ or $~~b = \sqrt{64}$ $b = -8~~$ or $~~b = 8$ Since the value of $b$ must be positive, $b = 8$