Posted by Claire on Friday, August 6, 2010 at 9:35pm.
8. Write the equation for simple harmonic motion given that the amplitude is 5 centimeters and the frequency is 2/ ð cycles per second. Assume that the maximum displacement occurs when t = 0.
a. y = 5sin4t
b. y = 5cos2t
c. y = 5cos4t
d. y = 5sin2t
9. Write the equation for simple harmonic motion given that the amplitude is 4 centimeters and the period is ð seconds. Assume zero displacement at t = 0.
a. y = 4cos2ðt
b. y = 4sin2ðt
c. y = 4cos2t
d. y = 4sin2t
*How would go about solving these? Need Help.

trig  bobpursley, Friday, August 6, 2010 at 11:51pm
amplitude is pretty simple, that is the coefficent in front of the sin/cos term.
If it starts at zero amlitude at zero time, then it has to be sine
If it is maximum amplitude at zero time, it has to be cosine. Think out that.
Now the period. the standard format of the trig arguement is (2PI*frequency*time) I don't see PI in any of the answers, so I really don't understand.
on 8, with what I have given you, it has to be cosine, and the argument in the cosine term is 2PI*frequency*t
in 9, it has to be sine, with the argument 2PI*frequency*time.