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# C4 MEI Harmonic Form watch

1. Doing some questions on harmonic form and I am getting stuck in some places that I thought I understood in class.

What dictates which order your A and B are when you do arctan(B/A) ?
What dictates whether or not it's a + or a - in the translation of the X?

Question:
Spoiler:
Show
The question specifically, if you need it for your examples is:

Write each of the following functions in the form R cos (theta +- alpha), where R > 0 and alpha is acute.
(i) cos(theta) + sin(theta)
(ii)2cos(theta) - sin(theta)
(iii)31/2sin(theta) + cos(theta)
2. (Original post by drakansteal)
Doing some questions on harmonic form and I am getting stuck in some places that I thought I understood in class.

What dictates which order your A and B are when you do arctan(B/A) ?
What dictates whether or not it's a + or a - in the translation of the X?

Question:
Spoiler:
Show
The question specifically, if you need it for your examples is:

Write each of the following functions in the form R cos (theta +- alpha), where R > 0 and alpha is acute.
(i) cos(theta) + sin(theta)
(ii)2cos(theta) - sin(theta)
(iii)31/2sin(theta) + cos(theta)
, so, for example, in (i):

and and you take the (+) so you're using , hence:

Squaring the first two equations and adding:

Dividing the second equation by the first:

What equations would you get for (ii)?

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