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Ch. 1 - Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
All textbooksHass 15th EditionCh. 1 - FunctionsProblem 1.3.68
Chapter 1, Problem 1.3.68

General Sine Curves


For


f(x) = A sin ((2π/B)(x – C) +D


identify A, B, C, and D for the sine functions in Exercises 67–70 and sketch their graphs.


y = ½ sin (πx – x) + ½

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1
Step 1: Start by comparing the given sine function y = ½ sin(πx - x) + ½ to the general sine function f(x) = A sin((2π/B)(x - C)) + D. Notice that the given function has a simplified argument inside the sine function, so simplify πx - x to (π - 1)x.
Step 2: Identify the amplitude A. The amplitude is the coefficient of the sine function, which in this case is ½. Therefore, A = ½.
Step 3: Identify the period B. The period is determined by the coefficient of x inside the sine function. Here, the coefficient of x is (π - 1). The period B is calculated as B = 2π / |π - 1|.
Step 4: Identify the phase shift C. The phase shift is determined by the term (x - C) inside the sine function. Since there is no explicit constant added or subtracted from x in the argument, C = 0 (no horizontal shift).
Step 5: Identify the vertical shift D. The vertical shift is the constant added outside the sine function, which in this case is ½. Therefore, D = ½. With these values (A = ½, B = 2π / |π - 1|, C = 0, D = ½), you can now sketch the graph of the sine function.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Amplitude

The amplitude of a sine function, represented by 'A' in the equation f(x) = A sin(...), determines the height of the wave from its midline to its peak. It indicates how far the graph stretches vertically. In the given function, the amplitude is ½, meaning the maximum value of the sine wave will be ½ above and ½ below the midline.
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Period

The period of a sine function, determined by 'B' in the equation, indicates the length of one complete cycle of the wave. It is calculated using the formula Period = 2π/B. In the provided function, the coefficient of x inside the sine function affects how quickly the wave oscillates; a larger value of B results in a shorter period.
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Phase Shift and Vertical Shift

The parameters 'C' and 'D' in the sine function represent the phase shift and vertical shift, respectively. The phase shift, given by C, moves the graph left or right, while the vertical shift, represented by D, moves the graph up or down. In the function y = ½ sin(πx - x) + ½, the phase shift can be derived from the expression inside the sine function, and the vertical shift is +½, indicating the entire graph is shifted up by ½.
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Related Practice
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Textbook Question

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