Use the table to answer the question

X: 0, pi/2, pi, 3pi/2, 2pi
F(x) 1, 0, -1, 0, 1

The values of a sine function at intervals of pi/2 have been recorded in the table.
Identify the value of the phase shift (c) and write the equation of the function

1 answer

From the table provided, we can observe the values of the sine function at specific intervals:

  • \( F(0) = 1 \)
  • \( F(\frac{\pi}{2}) = 0 \)
  • \( F(\pi) = -1 \)
  • \( F(\frac{3\pi}{2}) = 0 \)
  • \( F(2\pi) = 1 \)

These correspond to the standard sine function, but the values suggest a cosine function due to the fact that the maximum occurs at \( x = 0 \).

We know that the sine function has the general form:

\[ F(x) = A \sin(B(x - c)) + D \]

Where:

  • \( A \) is the amplitude,
  • \( B \) affects the period,
  • \( c \) is the phase shift,
  • \( D \) is the vertical shift.

From the table, we can see a complete cycle of the sine function occurring from \( 0 \) to \( 2\pi \), which indicates a regular period, suggesting \( B = 1 \).

Since the maximum value occurs at \( x = 0 \), it is actually equivalent to the cosine function shifted. The cosine function can be expressed as:

\[ F(x) = A \cos(B(x - c)) + D \]

The maximum of the cosine function is \( A \) when \( x = 0 \), and since \( F(0) = 1 \), we have:

  • \( A = 1 \),
  • \( D = 0 \) (no vertical shift).

The cosine function has a maximum value at \( x = 0 \) when there is no phase shift, indicating:

\[ F(x) = \cos(x) \]

Thus, comparing to the standard sine function, we recognize that this can be reinterpreted using the sine function with a phase shift. The cosine function can also be expressed in terms of the sine function:

\[ \cos(x) = \sin\left(x + \frac{\pi}{2}\right) \]

Thus, the phase shift \( c \) is \( -\frac{\pi}{2} \) to rewrite the equation as:

\[ F(x) = \sin\left(x + \frac{\pi}{2}\right) \]

Putting this all together, we have:

  • Phase Shift (c): \( -\frac{\pi}{2} \)
  • Equation of the Function: \( F(x) = \sin\left(x + \frac{\pi}{2}\right) \)

This matches the values provided in the table.