Math and Motion

needs an editor (& proofreader)

I post this after reading less than 2% of this since the description of rounding has a detail which is awkward, silly, and WRONG [because the author misunderstands “round to even”]. E.g., if we round to zero decimal places, the author’s procedure would produce 7 from 7.50, 7.52, 7.54, 7.56, 7.58 [because 0, 2, 4, 6, 8 are even] and produce 8 from 7.51, 7.53, 7.55, 7.57, 7.59 [because 1, 3, 5, 7, 9 are odd] — truly bizarre. Hint: an online search for “round-to-even” can provide a clue to the author’s mistake.

On the other hand, the context for that blunder is a reasonable distinction between “precision” and “accuracy”, so my provisional rating is 2 stars rather just 1.

Further reading finds a mechanistic approach to algebra and a sloppy summary of trig. E.g.,the section on triangles emphasizes “The opposite side is the side that is on the opposite side of the triangle” and “The Hypotenuse is always the longest side of a triangle.” [That 2nd statement is a clue that this author only considers right triangles.]

In any event, somebody needs to fix the mobile version because the figures seen in the Mac version of the Triangle section do not appear on my iPad (even after deleting and re-downloading). Interactive 3.1 is a static stub — clue: two labels read “Loren ipsum”. Many statements omit key constraints: e.g., “Average speed equals the initial speed plus the final speed divided by two.” (hence, driving in stop-and-go traffic has zero MPH as its average speed ??). That’s enough reading for me to downgrade this to a negative-two star rating (not negative-five because a student who struggles to make sense of this mess may have learned some stuff).