Napoleon, on a river bank, wanted to know the width of the stream. a
young soldier faced directly across the stream and adjusted the visor of
his cap until the tip of the visor was in line with his eye and the opposite
bank. next he did an about-face and noted the spot on the ground now
in line with his eye and visor-tip. he paced off the distance to this spot,
made his report, and earned a promotion. what postulate is this method
based on? draw a diagram to you explain.