Pre calculus, vectors

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A straight river flows at a speed of 20km/h. A boater starts at the south shore and heads in ths direction of 70degrees from the shore. The boat has a speed of 20km/h in still water. Find the true speed and direction of the boat.

  • Pre calculus, vectors -

    Vb = 20km @ 70o + 20km @ 0o.

    Vb = X + Yi.
    Vb = (20*cos70*20) + (20*sin70)i
    Vb = 26.84 + 18.79i

    tanA = Y/X = 18.79/26.84 = 0.70022
    A = 35o = Direction.

    Vb = X/cosA = 26.84/cos35 = 32.8 km/h =
    Velocity of the boat.

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