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Question
Math
Posted 5 months ago

hh is a trigonometric function of the form h(x)=acos(bx+c)+dh(x)=a \cos (b x+c)+d.
Below is the graph of h(x)h(x). The function has a maximum point at (π2,5)\left(-\frac{\pi}{2}, 5\right) and a minimum point at (π4,4)\left(\frac{\pi}{4},-4\right).

Find a formula for h(x)h(x). Give an exact expression.
h(x)=
h(x)=
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Answer from Sia
Posted 5 months ago
Solution by Steps
step 1
Identify the amplitude of the function from the graph. The amplitude is the distance from the midline to the maximum or minimum value of the function
step 2
The amplitude is given by the difference between the maximum and minimum y-values divided by 2: a=5(4)2=92a = \frac{5 - (-4)}{2} = \frac{9}{2}
step 3
Determine the period of the function. The period is the distance on the x-axis to complete one full cycle
step 4
The period is given by the distance between two consecutive maximum points or two consecutive minimum points. From the graph, the period is 3π/23\pi/2
step 5
Relate the period of the function to the coefficient bb in the function h(x)=acos(bx+c)+dh(x) = a \cos(bx + c) + d. The period TT is given by T=2πbT = \frac{2\pi}{b}
step 6
Solve for bb using the period: b=2πT=2π3π/2=43b = \frac{2\pi}{T} = \frac{2\pi}{3\pi/2} = \frac{4}{3}
step 7
Identify the vertical shift dd by finding the midline of the function, which is the average of the maximum and minimum y-values
step 8
The vertical shift is d=5+(4)2=12d = \frac{5 + (-4)}{2} = \frac{1}{2}
step 9
Determine the phase shift by finding the value of cc. The graph shows a maximum at x=π/2x = -\pi/2, which corresponds to the cosine function's maximum at 00
step 10
Solve for cc using the fact that the maximum of the cosine function is at bx+c=0bx + c = 0. With b=43b = \frac{4}{3} and x=π/2x = -\pi/2, we have 43(π/2)+c=0\frac{4}{3}(-\pi/2) + c = 0
step 11
Solve for cc: c=43(π/2)=2π3c = \frac{4}{3}(\pi/2) = \frac{2\pi}{3}
step 12
Write the final function using the values of aa, bb, cc, and dd: h(x)=92cos(43x+2π3)+12h(x) = \frac{9}{2} \cos\left(\frac{4}{3}x + \frac{2\pi}{3}\right) + \frac{1}{2}
[1] Answer
h(x)=92cos(43x+2π3)+12h(x) = \frac{9}{2} \cos\left(\frac{4}{3}x + \frac{2\pi}{3}\right) + \frac{1}{2}
Key Concept
Determining the equation of a trigonometric function from its graph
Explanation
The equation of a trigonometric function can be determined by identifying the amplitude, period, phase shift, and vertical shift from its graph. These values correspond to the constants in the function's equation.

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