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**Lloyd W****Guest**

y = 15 cos (5t - ( 3pi / 2 ) )

Now I know that the amplitude is 15 (obviously)

but how do i work out the frequency and phase.???

ironicly i have the answers which are that the period (T) = 2pi/5 and the phase shift is 3pi/10 compared to y=15cos5t

but how do u do it?

please help me

**ryos****Member**- Registered: 2005-08-04
- Posts: 394

Plain old cosx has a period of 2π. The variable (t) inside of cos is multiplied by 5, which *compresses* the period. So, the answer is 2π/5

The shift is the quantity subtracted from the variable inside cos. It seems that the shift is divided by the coefficient of t, giving 3π/10. I don't know why this is, but I just varified it with a graphing program and it's true.

El que pega primero pega dos veces.

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**mikau****Member**- Registered: 2005-08-22
- Posts: 1,504

"Trig waves"? BLASPHEMY! >:-O

A logarithm is just a misspelled algorithm.

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