Question 740831
A man who can row in still water at 5 mph heads directly across a river flowing at 6 mph. 
At what angle to the line on which he is heading does he drift downstream (nearest degree)?
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Draw the picture:
Let his time across the river be x hrs.
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You have a right triangle with base = 6x
height (perpendicular distance across river) = 5x
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Note: Not sure what angle you want.
Angle he travels measured from his starting point is theta
and tan(theta) = 5x/6x = 5/6 
Theta = arctan(5/6) = 39.81 degrees.
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Cheers,
Stan H.
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