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Homework Help: 2 of 2-Trig

  1. Aug 18, 2005 #1
    2 of 2--Trig

    Kahleela starts the engine on her small airplane. The engine drives a prop with a radius of 8.5 feet and its centerline 11.5 feet above the ground. At idel, the prop rotates at a constant speed of @ 800 revs/minute. The height of one prop tip as a function of time is given by:
    h=11.5+8.5sin(800t), where h is the height in feet and t is the time in minutes. When t= 12 minutes, what is h?

    I came up with 7.3 feet......I was wrong....

    Where did I stray? :yuck:
  2. jcsd
  3. Aug 18, 2005 #2
    Radians and degrees? What is the answer?
    Last edited: Aug 18, 2005
  4. Aug 18, 2005 #3
    a. 4.1 ft
    b. 18.9 ft
    c. 7.3 ft
    d. 15.7 ft
  5. Aug 18, 2005 #4


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    Science Advisor

    12*800= 9600. Assuming that is in degrees, which seems most likely, sin(9600)= -0.8660. 8.5sin(9600)= -7.36 (is that where you got the "7.3"? Did you forget the last part?) 11.5+ 8.5sin(9600)= 4.14. The tip of the propellor is 4.14 feet off the ground.
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