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Trig

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A boat heads S 15 degrees E on a river that flows due west. the boat travels S 11 degrees W with a speed of 25 km per hour. Find the speed of the current and the speed of the still water.

This is due tomorrow.

  • Trig - ,

    Draw a vector AB , S15°E, showing the boat in still water.
    Draw BC, going West, showing the speed of the river.
    Join AC , the resultant vector.
    By simple calculation of angles,
    angle A = 26°
    angle B = 75°
    angle C = 79°

    I see two simple applications of the sine law

    for the speed of the river:
    a/sin26° = 25/sin75°
    a = 25sin26/sin75 = 11.35

    for the boat's speed in still water:
    c/ain79 = 25/sin75
    c = 25.406

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