SHM- WTF Is these ships Questions (1 Viewer)

[Gangstar1]

Can someone completely explain how to do these fucked up questions there starting to give me the shits. I dunno when to use sin or cos or how to find the time it takes for the fucken boat to arrive >.>

 

[mitchy_boy]

Give an example question?

 

[Gangstar1]

Give an example question?

http://www.hotimg.com/image/eYfpha5

how were did the pi pop up how do you knwo if you use sin or cos

 

[Trebla]

It doesn't matter whether you use sine or cosine. If you keep it generalised with either
x = asin(nt + α) + b
or
x = acos(nt + α) + b
then solving the α will automatically account for any differences between selecting sine or cosine. You can easily convert one to the other using the result sin(π/2 - θ) = cos θ or cos(π/2 - θ) = sin θ.

 

[funnytomato]

http://www.hotimg.com/image/eYfpha5

1 how were did the pi pop up
2 how do you knwo if you use sin or cos

1 for example, y=sinx has a period of 2pi, but if you multiply x by n i.e. y=sin(nx)
you're streching(or shrinking) the graph horizontally by a factor of 1/n
so the time for each cycle(a HORIZONTAL distance on the graph) also changes to 2pi*1/n , T=2pi/n , n=2p/T

2 the given infomation is about high and low tides at certain times , so you'd use cos function since it starts at its extreme values
in this example, you start at the minimum so you'd better use -a*cos(nt).
if the earlier time is the high tide , it's just the +ve cos function a*cos(nt)

 

[funnytomato]

also , in this question, the solution involves shifting axis so the equation becomes simpler

however,the catch is that you have to remember to adjust all the data accordingly as well

 

[maths lover]

Can someone completely explain how to do these fucked up questions there starting to give me the shits. I dunno when to use sin or cos or how to find the time it takes for the fucken boat to arrive >.>

may i ask what textbook this, i like the worked solutions.

 

[SpiralFlex]

may i ask what textbook this, i like the worked solutions.

The Cambridge Year 12 book.