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Which of the following is a general solution of the equation sin 2x = - rac{1}{2}? A - HSC - SSCE Mathematics Extension 1 - Question 11 - 2018 - Paper 1

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Which of the following is a general solution of the equation sin 2x = - rac{1}{2}? A. x = n rac{ ext{π}}{12} + (-1)^{n} rac{ ext{π}}{2} B. x = n rac{ ext{π}}{2}... show full transcript

Worked Solution & Example Answer:Which of the following is a general solution of the equation sin 2x = - rac{1}{2}? A - HSC - SSCE Mathematics Extension 1 - Question 11 - 2018 - Paper 1

Step 1

Determine the general solution for sin 2x = -1/2

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Answer

To solve the equation sin(2x)=12\sin(2x) = -\frac{1}{2}, we first find the angles which satisfy this condition. The sine function equals -1/2 at certain reference angles in the unit circle. These reference angles can be obtained from the sine function:

  1. The angles are given by:

    • 2x=7π6+2nπ2x = \frac{7\pi}{6} + 2n\pi
    • 2x=11π6+2nπ2x = \frac{11\pi}{6} + 2n\pi
  2. Dividing both sides of the equations by 2 gives:

    • x=7π12+nπx = \frac{7\pi}{12} + n\pi
    • x=11π12+nπx = \frac{11\pi}{12} + n\pi

This can be summarized in a general solution form depending on whether n is even or odd for the possible solutions.

Step 2

Identify the answer choices

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Answer

In the choices provided, we need to determine which of these aligns with our derived general solutions. After evaluating:

  • A. x=nπ12+(1)nπ2x = n\frac{\pi}{12} + (-1)^n\frac{\pi}{2} is not correct.
  • B. x=nπ2+(1)nπ12x = n\frac{\pi}{2} + (-1)^n\frac{\pi}{12} is not correct.
  • C. x=nπ2+(1)n+1π12x = n\frac{\pi}{2} + (-1)^{n+1}\frac{\pi}{12} seems plausible.
  • D. x=nπ12+(1)nπ2x = n\frac{\pi}{12} + (-1)^n\frac{\pi}{2} does not match either.

Therefore, option C is the correct choice as it encapsulates the derived general solutions.

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