Can someone please explain this to me?

Any help would be greatly appreciated!

Thanks in advance!

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- Jul 25th 2009, 12:51 PMs3aCosine/hyperbola qiestion
Can someone please explain this to me?

Any help would be greatly appreciated!

Thanks in advance! - Jul 25th 2009, 03:36 PMyeongil
(This is more of a Precalculus question, I think.)

Comparing this to the basic form:

The center is at (0, 0), a = 5, and b = 12. Use the Pythagorean relation

to solve for c:

The foci are at (c, 0) and (-c, 0), or (13, 0) and (-13, 0).

Now, we look at the form of the cosine function:

(I capitalized A, B & C so that you can see that they are different than the a, b & c I used for the hyperbola equation.)

The period of is , and can be found by finding the distance from one maximum to the next, which in our case is 26.

For our purpose we'll just use the positive value, .

In , one of the maximum is at (0, 1).

In , the corresponding maximum is at (0, A).

In our function, since one of the maxima is at (-13, A) (we don't know what A is yet), our function has a horizontal shift 13 units to the left, or :

At this point, we could solve for A, why bother? There's only one choice that matches our values for B & C, and that is choice (A).

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