So I'm having intelligent discussion with a pro high school geometry teacher, used to be an engineer, no mud-slinging, no vitriol, and yet we're not taking the same position. Imagine. Sounds like real math for a change. Not that I dislike the kind of rhetoric we indulge in here -- always enjoyed math-teach in measured doses, consider it a lively "making waves" kind of place, even if repetitive.
Anyway, what we're arguing about is whether text books should intentionally make errors to keep students on their toes. And if they do so, should this be kept secret, mentioned in the teacher's manual only? Because we don't want students to develop a kow-tow attitude, e.g. just because it's yellow and has the Springer-Verlag imprimatur (this text doesn't), doesn't mean it can't be wrong in some way.
We want that healthy "question authority" attitude, a prerequisite to any kind of functioning democracy (is my bias).
Here's a link to the exercise in question, clearly mis- labeled, and yet the teacher's opinion is the text does this on purpose, monkey's with "scale", precisely to remind students that drawings in the field are likewise fallible, i.e. don't believe everything you see in print (point taken).