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Calculus/Basic trigonometry.

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Expert: - 5/1/2009


Question
The problem says:

A lighthouse in Delaware Bay is known to be 120 feet tall. You use your sextant to measure the angle of elevation to the top of the lighthouse to be 10 degrees. How far from the lighthouse are you(to the nearest tenth)?

Answer

Lighthouse
Questioner:   jamal
Country:  United States
Category:  Calculus
Private:  No
 
Subject:  math problem
Question:  The problem says:
..........................................
Hi, Jamal,

Your question is a standard right-triangle trig exercise:

A lighthouse in Delaware Bay is known to be 120 feet tall. You use your sextant

>> Please! This is a family-oriented site.

to measure the angle of elevation to the top of the lighthouse to be 10 degrees. How far from the lighthouse are you(to the nearest tenth)?

......................
Draw a nice diagram. (see attached, assuming I remember)

Now, refer the sides to the angle of 10 degrees, (I will call it t.)

120 feet is opposite t.
x is adjacent to t.

Use the tangent function:
         120
tan 10 = -----
          x

Cross-multiply:
     120
x = ---------
   tan 10

Use your calculator now.  You can do the rest.

Paul Klarreich

Expertise

All topics in first-year calculus including infinite series, max-min and related rate problems. Also trigonometry and complex numbers, theory of equations, exponential and logarithmic functions. I can also try (but not guarantee) to answer questions on Analysis -- sequences, limits, continuity.

Experience

I taught all mathematics subjects from elementary algebra to differential equations at a two-year college in New York City for 25 years.

Education/Credentials
(See above.)

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