an airplane is heading due north at 800 km h when it encounters a wind from the northeast at 100km h what is the resultant velocity

The resultant is 732.7 km/h on a heading 5.5° west of north.

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Some graphing calculators handle vector addition better than others. For this TI-83/84, it is convenient to define the variable D as π/180, so it converts degrees to radians. The resulting exponential shows the angle in degrees because the calculator is in Degrees mode.