### Home > CCG > Chapter 5 > Lesson 5.3.2 > Problem5-90

5-90.

Find the length of $\overline{DF}$ in the diagram from problem 5-89 if $DE=9$ mm.

Find the measure of the unknown angle and place the given information on a diagram.

Use the Law of Sines. See the Math Notes box for this lesson.

$\frac{\sin54º}{9}=\frac{\sin72º}{x}$

Solve for $x$.