From the diagram below, if the measure of < C = 30 °, and side BC = 15, then side AB = _____.

To solve this problem, we will use the trigonometric function tangent.
Recall that by definition, in a right triangle:
[tex]tan\theta=\frac{opposite\text{ leg}}{adjacent\text{ leg}}.[/tex]Therefore:
[tex]tan30^{\circ}=\frac{AB}{15}.[/tex]Solving for AB, we get:
[tex]AB=tan30^{\circ}\times15.[/tex]Finally, we get:
[tex]AB=5\sqrt{3}.[/tex]