Assume the river’s width is 0. Then put a straight line between A and B. Restore river’s width. Make bridge at the intersection of the AB and the zero-width river.

Экскьюз май френч.

]]>I found 2 copies of Volume 1 (actually, one was without volume # at all, must have been the very first printing), and we are planning to read and discuss. Thanks for pointing us to Yaglom – he looks fun.

]]>Instead, how about moving point A down by a distance equal to the width of the river and perpendicular to it? The shortest path is now a straight line, and we draw the bridge upwards from where the line intersects the bottom of the river.

]]>In regular English, a ruler is a stick used to measure length. It has a straight edge, and it has markings, eg in eighths of inches.

For construction only, a ruler is a stick with two parallel sides. It should not be marked, or the markings should be ignored. Many good constructions can be performed with only a ruler (no compass).

BTW, I found all three volumes on my shelf. I will propose to a friend that we read and solve together – a little joint study to keep the brains nimble. Thanks for recommending.

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