Minor mathematical error in trunk/book.tex

[guanidene]

On line 454 of trunk/book.tex

a cosine signal with {\tt offset=pi/2} is identical to a sine

should change to

a sine signal with {\tt offset=pi/2} is identical to a cosine

or

a cosine signal with {\tt offset=-pi/2} is identical to a sine

Kindly forgive me if this is not the correct way to report such issues

[AllenDowney]

That's a fine way to report such issues.

This one is fixed now. Thanks!

1236a9e