## Elementary Geometry for College Students (6th Edition)

We use trigonometry: Altitude 1 $= \frac{21}{sin90^{\circ}}=21$ For the second altitude, we use the angle in the lower right hand corner, which we call x: $sinx = \frac{BF}{21} \\ 3/5 = BF/21 \\ BF = 63/5$