Answer:
The cosine function to model the height of a water particle above and below the mean water line is h = 2·cos((π/30)·t)
Step-by-step explanation:
The cosine function equation is given as follows h = d + a·cos(b(x - c))
Where:
 = Amplitude
 = Amplitude
2·π/b = The period
c = The phase shift
d = The vertical shift
h = Height of the function
x = The time duration of motion of the wave, t
The given data are;
The amplitude  = 2 feet
 = 2 feet
Time for the wave to pass the dock 
The number of times the wave passes a point in each cycle = 2 times
Therefore;
The time for each complete cycle = 2 × 30 seconds  = 60 seconds
The time for each complete cycle = Period = 2·π/b = 60
b = π/30 =
Taking the phase shift as zero, (moving wave) and the vertical shift as zero (movement about the mean water line), we have
h = 0 + 2·cos(π/30(t - 0)) = 2·cos((π/30)·t)
The cosine function is h = 2·cos((π/30)·t).
 
        
             
        
        
        
I assume by starting value, you mean y-intercept. The y-intercept is 15
To find this, we need to use slope intercept form and the given information to find it. 
y = mx + b ----> plug in the known values
9 = -3/4(8) + b
9 = -6 + b
15 = b
Therefore, the starting value is 15.
 
        
             
        
        
        
Answer:
B
Step-by-step explanation:
The dot on 2 is an open spot, so 2 isn't part of the solution. the arrow points towards +∞ so, yeah. b
 
        
             
        
        
        
Answer:
a
Step-by-step explanation: cause
 
        
             
        
        
        
 Answer: y=4/5x-2 or y=4/5x+(-2)
Step-by-step explanation:
The formula for slope-intercept form is y=mx+b.
To find the slope, we can use the formula  and plugging in the points given.
 and plugging in the points given.

We know our slope is 4/5. We can plug this into our slope-intercept form and then plug in a point to find b, y-intercept.




We know the y-intercept is -2.
THe final equation is y=4/5x-2 or y=4/5x+(-2).