trig functions translations and combinations of transfomatio

[Guest]

Hi, I really need help with this question

1) the water depth in a harber is 21m at hight tide, and 11m at low tide. One cycle is completed approximatly every 12h.

a) find an equation for the water depth as a function of the time, t hours, after low tide
b) Draw a graph 48h after low tide, witch occured at 14:00

y=asink(x-c)+d

Amplitude
a=21-11/2
a=5

K

p=2pi/k
12=2pi/k
k=2pi/12
k=pi/6

what about the c and the d??

and does anyone know of anygood software to graph trig functions?

Thanks

 

[skeeter]

d is the mean water height between high and low tide ...

d = (21+11)/2 = 16

since low tide is at 1400, it also occurs at 0200, 12 hours prior

if t = 0 is 0000 ...

h = -5cos[(pi/6)(t - 2)] + 16

or

h = 5sin[(pi/6)(t - 5)] + 16

 

[Guest]

^ ok thank you!