## Basic College Mathematics (10th Edition)

The unknown length of the triangle $\approx 17.1$ km
Let $x =$ unknown length of the triangle $a^{2} + b^{2} = c^{2}$ $x^{2} + 13.2^{2} = 21.6^{2}$ $x^{2} + 174.24 = 466.56$ $x^{2} = 292.32$ $x = \sqrt 292.32$ $x = 17.097...$ $x \approx 17.1$ km