# Trigonometry..

posted by .

During high tide the water depth in a harbour is 22 m and during low tide it is 10m(Assume a 12h cycle).
Calculate the times at which the water level is at 18m during the first 24 hours.

My solution:
first I found the cos equation: H(t)=-6cos(π/6t)+16
then..
Let π/6t=Θ
18=-6cosΘ+16
18-16=-6cosΘ
Θ=1.230959417

Then I don't know what's next....

• Trigonometry.. -

H(t)=-6\cos(\frac{\pi}{6} t)+16

• Trigonometry.. -

cosΘ < 0 in QII and QIII
arccos(-1/3) = 1.91 = pi-1.23
or pi+1.23 = 4.37

So, t = (6/pi) * (1.91 or 4.37)
t = 3.64 or 8.35 hours

## Similar Questions

1. ### Trigonometry

At the ocean, it is known that the tide follows a trigonometric path. At high tide, the water comes in to a point 1 meter from where I placed a flag. At low tide, the water comes in to a point 11 meters from the same flag. The time …
2. ### Trig problem

During a 12- hour period, the tides in one area of the Bay of Fundy causes the water level to rise to 6 m above the average sea level and to fall 6 m below average sea level. The depth of the water at low tide is 2m as measured against …
3. ### trig question

During a 12- hour period, the tides in one area of the Bay of Fundy causes the water level to rise to 6 m above the average sea level and to fall 6 m below average sea level. The depth of the water at low tide is 2m as measured against …
4. ### Math

The Distance from the top of a cliff to the water below ranges from 13m(low tide) to 8m(high tide). Low tide occurs at 12:00 noon and it takes six hours between low tide and high tide. a)Develop an equation representing the distance …
5. ### science help plzzz

1. Which of the following statements best defines tides?
6. ### Science - Check my answers

1. Which of the following statements best defines tides?
7. ### Trigonometric Functions

The average depth of the water in a port on a tidal river is 4m. At low tide, the depth of the water is 2m. One cycle is completed approximately every 12h. a)Find an equation of the depth, d(t)metres, with respect to the average depth, …
8. ### Trig functions

The average depth of the water in a port on a tidal river is 4m. At low tide, the depth of the water is 2m. One cycle is completed approximately every 12h. a)Find an equation of the depth, d(t)metres, with respect to the average depth, …
9. ### Science "check my "answers"

1. Which of the following statements best defines tides?
10. ### Math

3. At the end of a dock, high tide of 14 m is recorded at 9:00 a.m. Low tide of 6 m is recorded at 3:00 p.m. A sinusoidal function can model the water depth versus time. a) Construct a model for the water depth using a cosine function, …

More Similar Questions