# Thread: "The Complete Idiot's Guide to Calculus" - An error?

1. ## "The Complete Idiot's Guide to Calculus" - An error?

Hey guys, I'm reading The Complete Idiot's Guide to Calculus and I think the book made a mistake.

Here is a picture of a graph that the author claims to have "origin-symmetry":

And here is his description of this graph. When the author mentions Figure 3.4, he is mentioning the graph he claims to have "origin-symmetry".

Origin-symmetry is achieved when the graph does exactly the opposite thing on either
side of the origin. In Figure 3.4, notice that the origin-symmetric curve snakes down and
to the right as x gets more positive, and up and to the left as x gets more negative. In fact,
every turn in the second quadrant is matched and inverted in the fourth quadrant.
To me, it looks like it actually has y-symmetry!

If it had origin-symmetry, the graph to the right of the origin should be in quadrant 4, not quadrant 1! Because when x>0, y must be negative. And when x<0, y must be positive.

And when the author says "the origin-symmetric curve snakes down and to the right as x gets more positive", you can plainly see that the curve actually snakes up and to the right when x gets more positive

Is this book actually wrong on this subject?

2. Hello XRaptor
Originally Posted by XRaptor
Hey guys, I'm reading The Complete Idiot's Guide to Calculus and I think the book made a mistake.

Here is a picture of a graph that the author claims to have "origin-symmetry":

And here is his description of this graph. When the author mentions Figure 3.4, he is mentioning the graph he claims to have "origin-symmetry".

To me, it looks like it actually has y-symmetry!

If it had origin-symmetry, the graph to the right of the origin should be in quadrant 4, not quadrant 1! Because when x>0, y must be negative. And when x<0, y must be positive.

And when the author says "the origin-symmetric curve snakes down and to the right as x gets more positive", you can plainly see that the curve actually snakes up and to the right when x gets more positive

Is this book actually wrong on this subject?

You are right; the book is wrong. This graph has symmetry about the $\displaystyle y$-axis.

A graph that has origin-symmetry can be rotated about the origin through $\displaystyle 180^o$, and the new position matches exactly the original graph.

Don't blame the authors too much - we all make mistakes!

Hello XRaptorYou are right; the book is wrong. This graph has symmetry about the $\displaystyle y$-axis.

A graph that has origin-symmetry can be rotated about the origin through $\displaystyle 180^o$, and the new position matches exactly the original graph.

Don't blame the authors too much - we all make mistakes!

Since the book is for complete idiots, I doubt the authors would be expecting any of their mistakes to be spotted .... So the authors escape clause is that anyone spotting a mistake is obviously excluded from the intended audience.

4. Originally Posted by mr fantastic
Since the book is for complete idiots, I doubt the authors would be expecting any of their mistakes to be spotted .... So the authors escape clause is that anyone spotting a mistake is obviously excluded from the intended audience.
Roflmao!

5. Originally Posted by mr fantastic
Since the book is for complete idiots, I doubt the authors would be expecting any of their mistakes to be spotted .... So the authors escape clause is that anyone spotting a mistake is obviously excluded from the intended audience.
Mmm...yes. The problem is that, even if you start out as one, as soon as you begin to read and understand, you're no longer a complete idiot ... So perhaps you shouldn't get past the first page...