Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 6 - Section 6.2 - Trigonometry of Right Triangles - 6.2 Exercises - Page 489: 65

Answer

$5808ft$

Work Step by Step

Step 1. Draw a diagram as shown in the figure (not to scale) where h is the height of the mountain, BC=1000ft Step 2. As $AD\parallel BE$, we have $ \angle ABE=32^\circ$ and $ \angle ACE=35^\circ$ Step 3. In the right triangle of $\Delta ABE$, we have $tan32^\circ=\frac{h}{BE}$ and $BE=h\cdot cot32^\circ$ Step 4. In the right triangle of $\Delta ACE$, we have $tan35^\circ=\frac{h}{CE}$ and $CE=h\cdot cot35^\circ$ Step 5. As BC=1000ft, we have BE−CE=BC and $h\cdot cot32^\circ-h\cdot cot35^\circ=1000$ Step 6. Solve the above equation as$(cot32^\circ-cot35^\circ)h=1000$ or $(1.60033−1.42815)h=1000$ which gives $h\approx5808ft$
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