Math Problem Statement

Jasmine is converting f(x) = -sin(2x + π/4) - 1 to a cosine function. Her first step was to rewrite the function as f(x) = -sin(2(x + π/8)) - 1. What transformation does she need to apply?

Solution

To determine the required transformation Jasmine needs to apply, we must analyze the given function and the changes made:

  1. The original function is f(x)=sin(2x+π4)1f(x) = -\sin\left( 2x + \frac{\pi}{4} \right) - 1.
  2. Jasmine's first step is rewriting it as f(x)=sin(2(x+π8))1f(x) = -\sin\left( 2\left(x + \frac{\pi}{8} \right)\right) - 1.

To convert a sine function to a cosine function, we recognize that a cosine function is essentially a sine function shifted by π2\frac{\pi}{2}. In this case, the argument of the sine function is 2x+π82x + \frac{\pi}{8}, and we need to shift the sine function horizontally by an appropriate amount to make it match the cosine form.

Upon comparing the sine and cosine forms:

  • The argument of the sine function in Jasmine's equation is 2(x+π8)2\left(x + \frac{\pi}{8}\right).
  • The argument of the cosine function should be 2(xπ8)2\left(x - \frac{\pi}{8}\right), which suggests the shift is to the right.

Therefore, the correct transformation is to shift the graph π8\frac{\pi}{8} units to the right.

Answer: Option #3. Jasmine needs to shift the graph an additional π4\frac{\pi}{4} units to the right to obtain the cosine function f(x)=cos(2(xπ8))1f(x) = -\cos\left( 2\left(x - \frac{\pi}{8} \right)\right) - 1.

Would you like further clarification or additional steps? Here are some related questions for further exploration:

  1. How does a phase shift affect the graph of a sine or cosine function?
  2. What is the general formula for converting a sine function to a cosine function?
  3. How do amplitude and vertical shifts impact the graph of trigonometric functions?
  4. What is the difference between a horizontal shift and a phase shift in trigonometric functions?
  5. How do the coefficients in front of xx and within the parentheses affect the period of sine and cosine functions?

Tip: When converting between sine and cosine functions, always remember that the phase shift represents a horizontal translation and is related to the argument of the trigonometric function.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Graph Transformations
Phase Shift

Formulas

sin(x) = cos(x - π/2)
f(x) = a * sin(b(x - c)) + d
f(x) = a * cos(b(x - c)) + d

Theorems

Phase Shift Theorem

Suitable Grade Level

Grades 10-12