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Math Help - non right angle trig

  1. #1
    mat
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    non right angle trig

    A tanker is moving 5 nautical miles (5 knots) on bearing 105 degrees.at 1100 hours (11am) the tanker obserbs a lighthouse on bearing 040 degrees. at midday the lighthouse bears 340 degrees. Draw a well labelled diagram to show the movement of the tanker between 11am and midday. calculate the distance in nautical miles from the tanker to the lighthouse at midday.


    I know the angle LH is 40 degrees
    but i still get confused in finding the angles for P1200 and P1100.
    The length from P1100 to P1200 is 5nm. I use the SIN rule for non right angle trig.
    so
    SIN 5nm SIN ??????
    sin 40degrees equals sin ??????
    How do I work this out?
    I need the answer 12 hours from now
    thanks.
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  2. #2
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    Quote Originally Posted by mat View Post
    A tanker is moving 5 nautical miles (5 knots) on bearing 105 degrees.at 1100 hours (11am) the tanker obserbs a lighthouse on bearing 040 degrees. at midday the lighthouse bears 340 degrees. Draw a well labelled diagram to show the movement of the tanker between 11am and midday. calculate the distance in nautical miles from the tanker to the lighthouse at midday.


    I know the angle LH is 40 degrees
    but i still get confused in finding the angles for P1200 and P1100.
    The length from P1100 to P1200 is 5nm. I use the SIN rule for non right angle trig.
    so
    SIN 5nm SIN ??????
    sin 40degrees equals sin ??????
    How do I work this out?
    I need the answer 12 hours from now
    thanks.
    let lighthouse be point L

    1100 position ... point A

    1200 position ... point B

    m\angle A = 65

    m\angle B = 55

    m\angle L = 60

    use the law of sines ...

    \frac{LB}{\sin(65)} = \frac{AB}{\sin(60)}
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