Question

Help!?!?!?

The equation y = 7 cos((pi/3)t) models the height h in centimeters after t seconds of a weight attached to the end of a spring that has been stretched and then released.

a. Solve equation for t.
b. Find the times at which the weight is first at a height of 1 cm, of 3 cm, and of 5 cm above the rest position. Round your answers to the nearest hundredth.
c. Find the times at which the weight is at a height of 1 cm, of 3 cm, and of 5 cm below the rest position for the second time. Round your answers to the nearest hundredth.

(I already have A and B, i just have a question

Answer 1

For c, wouldnt the results be the same as b? What do i do differently on C? Do i just make 1, 3, and 5 negative or is it not that simple?

Answer 2

for C you find the period of the sine wave.
the 2nd time it'll reach those heights = 1st time + time period.

Answer 3

Can you show me? I still dont really get it. (Im not good at math at all!) :(

Answer 4

ok, time period of a sine wave y=A cos (wt)
is T = 2pi/w
here w=pi/3, right ?
so, T = 2pi/(pi/3) = 6 sec

so, 2nd time the height will be 2cm at 1.36+6 = 7.36 sec.
got this ?

Answer 5

yes.

Answer 6

Oh ok. I get it now. Thanks!!! :)

Answer 7

welcome ^_^