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March 26, 2017

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Two airplanes take off from an airport at the same time. One travels on a heading of 45 at 420 mph and the other on a heading of 150 at 400 mph. After two hours, how far apart are the airplanes?

A.650.66 miles
B.1,160 miles
C.1,301 miles

  • Pre-Cal - ,

    Use the cosine law, I got 650.66

  • Pre-Cal - ,

    Can you tell me how you did it? I got 5 more questions like this one.

  • Pre-Cal - ,

    are you not familar with the cosine law?
    You must have learned this to be able to do this kind of question.

  • Pre-Cal - ,

    Yes I am, but I don't understand it. I don't have a teacher to teach me. I do my work online, and I just need 2nd semester of pre-cal to graduate.

  • Pre-Cal - ,

    x^2 = 420^2 + 400^2 - 2(420)(400)cos 105°
    do the arithmetic

    I got 105° from the difference between 150° and 45°

  • Pre-Cal - ,

    thanks

  • Pre-Cal - ,

    d1 = 420mi/h[45o] * 2h = 840mi[45o]

    d2 = 400mi/h[150o] * 2h = 800mi[150o]

    D = 840[45o] - 800[150o]

    X = 840*Cos45 - 800*cos150 = 1287 mi
    Y = 840*sin45 - 800*sin150 = 194 mi

    D = sqrt(1287^2+194^2) = 1301.5 mi

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