Question

I've noticed in reading "G" that equations (18) and (19) are skipped even though (19) is used to solve for A and phi.
Could someone please list the missing equations so I can write them in the reading?
Thanks.

Answer 1

Based on their explanation,perhaps (18) is the unlabeled equation in "Proof of the Equivalence of (15) and (16), and (19) is the following unlabeled equations.

Or perhaps the reference to (19) is a typo, and they meant (17). This makes the most sense.

The idea is to change
a sin(kx) + b cos(kx) to an equivalent sin (or cos if you like).

For what it is worth, here is another derivation of this approach
http://mymathforum.com/algebra/28636-curiosity-proof-sin-x-b-cos-x-r-sin-x.html

Answer 2

Cool, thank you. That is very helpful. With those equations being as you said, that makes a lot more sense.