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square or rectangle ? Envisioning Information, page 84

I am reading the "Envisioning Information" (eighth printing). On the right side of page 84, there is a illustration of the "Pythagorean" theorem from the classical Chinese book "Chou Pei Suan Ching". The small center square in the induction equation looks more like a rectangle to me. Is this a mistake in the re-drawing or a visual effect? (I attempted to measure with a ruler, it seems the vertical is shorter than the horizontal, but not sure)

I am more curious what contributes to such a visual impression if it is indeed a true square


-Xiaoying Lin

-- Xiaoying Lin (email)

Xiaoying Lin is correct; the "square" is unsquare. It appears that the 2 verticals are misaligned; those 2 errors cumulate rather than cancel, resulting in the unsquare.

I'll fix this in the next printing of Envisioning Information.

The nice thing about writing an intense book is that you'll get intense readers!

-- Edward Tufte

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