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# what the hell is a math period?

HeySmall Christmas-Man!Registered User regular
edited January 2007
i'm studying for the Math B Regents in NYC, and I have no idea what the hell this is. It's been so long since I had the class.

i hear something about 2 pi, but what is that?

http://www.nysedregents.org/testing/mathre/regentmathb.html

http://www.nysedregents.org/testing/mathre/b806.pdf

for reference

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Starting to get dizzy Registered User regular
edited January 2007
A periodic function is one that oscillates (goes up and down) with a certain frequency, and repeats its values after the period has passed. For the function sinx, the period is 2*pi. The reason for this is sinx=0 at x=0, is 1 at x=pi/2, 0 again at pi, -1 at 3*pi/2, and 0 again at 2*pi, at which point it starts repeating itself. What you have to do is figure out how the 2 and 1/3 factors in the equation affect the period, if they do.

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edited January 2007
If you graph the function, you'll get a sin wave. The period is the total distance of a single oscillation.

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Registered User regular
edited January 2007
ASin(Bx+(-C))
Amplitude = |A|
Period = (2pi/B)
Phase Shift = C/B (IIRC, it might be just C).

So in this case it would be
[spoiler:31469e0d09]
Period = (2pi/(1/3))
which would equal 6pi [/spoiler:31469e0d09]

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Registered User regular
edited January 2007
Mrcheesypants beat me to it, but for the sake of completeness,
[spoiler:52749a00ab]The 2 has nothing to do with the period. It's the amplitude, which means that the peaks and troughs will be twice as high as a normal sine graph.[/spoiler:52749a00ab]

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Hey Small Christmas-Man!Registered User regular
edited January 2007
so i just multiply 2pi by whatever number is next to the x?

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Registered User regular
edited January 2007
so i just multiply 2pi by whatever number is next to the x?

Close. If you have sin bx (for variable x and some constant b), the period is 2*pi / b. It makes sense if you think about it. That is, dividing x by three uses values of x closer to the y-axis, so the period is longer (it takes smaller x values, so it takes longer to get through a whole cycle).

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