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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{π}{12} + (-1)^{n} rac{π}{12} B. x = n rac{π}{2} + (-1)^{n} rac{π... 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

Which of the following is a general solution of the equation sin 2x = - rac{1}{2}?

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Answer

To find the general solution for the equation sin(2x)=12\sin(2x) = -\frac{1}{2}:

  1. Identify the angles: The sine function equals 12-\frac{1}{2} at specific angles. These angles are typically 7π6\frac{7\pi}{6} and 11π6\frac{11\pi}{6} in the range from 00 to 2π2\pi.

  2. General form: The general solutions can be expressed as:

    • For 7π6\frac{7\pi}{6}: x=7π12+nπx = \frac{7\pi}{12} + n\pi (since sin\sin has a period of π\pi)
    • For 11π6\frac{11\pi}{6}: x=11π12+nπx = \frac{11\pi}{12} + n\pi
  3. Combine results: When combining these with the factor (1)n(-1)^{n} due to periodicity, we arrive at the most comprehensive general solution format.

Thus, the answer is C: x=nπ2+(1)nπ12x = n\frac{\pi}{2} + (-1)^{n} \frac{\pi}{12} where nn is any integer.

Step 2

Which function, in terms of time t, could represent the motion of the particle?

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Answer

In simple harmonic motion, the general form of displacement can be expressed as:

  1. Understanding displacement and velocity: Given the relation v2=n2(2ktx2)v^{2} = n^{2}(2kt - x^{2}), we recognize that a typical solution is either a sine or cosine function.

  2. Position function: The displacement function of a particle in harmonic motion can be expressed as a sine function:

    • Given the form resembles oscillatory motion, we can assume x(t)=Asin(nt+ϕ)x(t) = A\sin(nt + \phi) where AA is the amplitude and ϕ\phi is the phase shift.
  3. Evaluate options: Considering the given options:

    • A. x=kcos(nt)x = k\cos(nt) is valid but depends on the phase.
    • B. x=ksin(nt)x = k\sin(nt) fits well.
    • C. x=2kcos(nt)kx = 2k\cos(nt) - k includes a constant adjustment.
    • D. x=2ksin(nt)+kx = 2k\sin(nt) + k does as well, but might need further analysis.

Thus, the most versatile choice in harmonic models, considering amplitude is B: x=ksin(nt)x = k \sin(nt).

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