The graph of a sinusoidal function intersects its midline at (0,−7) and then has a minimum point at (4π,−9).Write the formula of the function, where x is entered in radians.
Q. The graph of a sinusoidal function intersects its midline at (0,−7) and then has a minimum point at (4π,−9).Write the formula of the function, where x is entered in radians.
Determine Amplitude: Determine the amplitude of the function.Since the midline is at y=−7 and the minimum point is at y=−9, the amplitude is the distance from the midline to the minimum, which is 2 units.Amplitude (A) = ∣midline−minimum∣=∣−7−(−9)∣=2
Identify Midline: Identify the midline D of the function.The midline is given as y=−7.D=−7
Determine Period: Determine the period T of the function.Since the function reaches its minimum at 4π and the next similar point (maximum or minimum) would be after a full period, we can infer that the period is 4 times the x-coordinate of the minimum point.T=4×(4π)=π
Calculate Value of B: Calculate the value of B using the period.The period T is related to B by the formula T=B2π.π=B2πB=2
Determine Phase Shift: Determine the phase shift C. Since the function intersects its midline at (0,−7), there is no horizontal shift, so the phase shift C is 0. C=0
Choose Sinusoidal Function: Choose the correct sinusoidal function.Because the function has a minimum point at (π/4,−9), we should use a cosine function that starts at a maximum. However, since we have a minimum point, we need to reflect the cosine function over the midline. This means we will use a negative cosine function.f(x)=−Acos(Bx+C)+D
Write Final Equation: Write the final equation of the sinusoidal function.Substitute the values of A, B, C, and D into the equation.f(x)=−2cos(2x)−7
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