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Which of the following is not equivalent to 
csc ((2pi)/(7)) ?

csc(-(12 pi)/(7))

csc ((16 pi)/(7))

csc ((12 pi)/(7))

csc ((19 pi)/(7))

Which of the following is not equivalent to csc2π7 \csc \frac{2 \pi}{7} ?\newlinecsc(12π7) \csc \left(-\frac{12 \pi}{7}\right) \newlinecsc16π7 \csc \frac{16 \pi}{7} \newlinecsc12π7 \csc \frac{12 \pi}{7} \newlinecsc19π7 \csc \frac{19 \pi}{7}

Full solution

Q. Which of the following is not equivalent to csc2π7 \csc \frac{2 \pi}{7} ?\newlinecsc(12π7) \csc \left(-\frac{12 \pi}{7}\right) \newlinecsc16π7 \csc \frac{16 \pi}{7} \newlinecsc12π7 \csc \frac{12 \pi}{7} \newlinecsc19π7 \csc \frac{19 \pi}{7}
  1. Properties and Periodicity: Understand the properties of the cosecant function and periodicity.\newlineThe cosecant function, csc(θ)\csc(\theta), is the reciprocal of the sine function, sin(θ)\sin(\theta), and has a period of 2π2\pi. This means that csc(θ+2πk)=csc(θ)\csc(\theta + 2\pi k) = \csc(\theta) for any integer kk.
  2. Analyze Option 11: Analyze the first option csc(12π7)\csc\left(-\frac{12 \pi}{7}\right). Using the property that csc(θ)=csc(θ)\csc(-\theta) = -\csc(\theta) and the periodicity of the cosecant function, we can find an equivalent angle in the positive direction by adding 2π2\pi until we get a positive angle. csc(12π7)=csc((2π12π7)+2πk)\csc\left(-\frac{12 \pi}{7}\right) = \csc\left(\left(2\pi - \frac{12\pi}{7}\right) + 2\pi k\right) for k=1k = 1, since we want the smallest positive coterminal angle. \csc\left(-\frac{\(12\) \pi}{\(7\)}\right) = \csc\left(\left(\frac{\(14\)\pi}{\(7\)} - \frac{\(12\)\pi}{\(7\)}\right) + \frac{\(14\)\pi}{\(7\)}\right) = \csc\left(\left(\frac{\(2\)\pi}{\(7\)}\right) + \frac{\(14\)\pi}{\(7\)}\right) = \csc\left(\frac{\(16\)\pi}{\(7\)}\right)
  3. Analyze Option \(2: Analyze the second option csc(16π7)\csc\left(\frac{16 \pi}{7}\right). Using the periodicity of the cosecant function, we can subtract 2π2\pi to find an equivalent angle. csc(16π7)=csc(16π72π)=csc(16π714π7)=csc(2π7)\csc\left(\frac{16 \pi}{7}\right) = \csc\left(\frac{16\pi}{7} - 2\pi\right) = \csc\left(\frac{16\pi}{7} - \frac{14\pi}{7}\right) = \csc\left(\frac{2\pi}{7}\right) This is equivalent to the original expression csc(2π7)\csc\left(\frac{2\pi}{7}\right).
  4. Analyze Option 33: Analyze the third option csc(12π7)\csc\left(\frac{12 \pi}{7}\right). Using the periodicity of the cosecant function, we can subtract 2π2\pi to find an equivalent angle. csc(12π7)=csc(12π72π)=csc(12π714π7)=csc(2π7)\csc\left(\frac{12 \pi}{7}\right) = \csc\left(\frac{12\pi}{7} - 2\pi\right) = \csc\left(\frac{12\pi}{7} - \frac{14\pi}{7}\right) = \csc\left(-\frac{2\pi}{7}\right) Since csc(θ)=csc(θ)\csc(-\theta) = -\csc(\theta), this is not equivalent to csc(2π7)\csc\left(\frac{2\pi}{7}\right) because the cosecant function is not an even function.
  5. Analyze Option 44: Analyze the fourth option csc(19π7)\csc\left(\frac{19 \pi}{7}\right). Using the periodicity of the cosecant function, we can subtract 2π2\pi multiple times to find an equivalent angle. csc(19π7)=csc(19π72π)=csc(19π714π7)=csc(5π7)\csc\left(\frac{19 \pi}{7}\right) = \csc\left(\frac{19\pi}{7} - 2\pi\right) = \csc\left(\frac{19\pi}{7} - \frac{14\pi}{7}\right) = \csc\left(\frac{5\pi}{7}\right) This is not equivalent to csc(2π7)\csc\left(\frac{2\pi}{7}\right) because 5π7\frac{5\pi}{7} is not a coterminal angle of 2π7\frac{2\pi}{7}.
  6. Determine Non-equivalent Option: Determine which option is not equivalent to csc(2π7)\csc\left(\frac{2\pi}{7}\right). From the previous steps, we have determined that csc(16π7)\csc\left(\frac{16 \pi}{7}\right) and csc(12π7)\csc\left(-\frac{12 \pi}{7}\right) are equivalent to csc(2π7)\csc\left(\frac{2\pi}{7}\right). However, csc(12π7)\csc\left(\frac{12 \pi}{7}\right) simplifies to csc(2π7)\csc\left(-\frac{2\pi}{7}\right), which is not equivalent to csc(2π7)\csc\left(\frac{2\pi}{7}\right). Therefore, csc(12π7)\csc\left(\frac{12 \pi}{7}\right) is not equivalent to csc(2π7)\csc\left(\frac{2\pi}{7}\right).

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