Solved on Feb 22, 2024

Find the true statement about the cotangent function y=cotxy=\cot x.
A. Zeros are nπ2\frac{n \pi}{2} where nn is an integer. B. Domain excludes xx where cosx=0\cos x=0. C. Principal cycle is on (π2,π2)\left(-\frac{\pi}{2}, \frac{\pi}{2}\right). D. Infinitely many vertical asymptotes at x=nπx=n \pi where nn is an integer.

STEP 1

Assumptions
1. The function given is y=cotxy = \cot x.
2. We need to evaluate the truthfulness of each statement regarding the properties of the cotangent function.

STEP 2

Evaluate statement A: The zeros of y=cotxy=\cot x are of the form nπ2\frac{n \pi}{2} where nn is an integer.
The cotangent function, cotx\cot x, is defined as cotx=cosxsinx\cot x = \frac{\cos x}{\sin x}. The zeros of the cotangent function occur when the numerator, cosx\cos x, equals zero, which is not correct. The zeros occur when the denominator, sinx\sin x, equals zero. Therefore, we need to find the values of xx for which sinx=0\sin x = 0.

STEP 3

Solve for the zeros of sinx\sin x.
The sinx\sin x function has zeros at x=nπx = n\pi where nn is an integer. This is because the sine function is zero at integer multiples of π\pi.

STEP 4

Compare the zeros of sinx\sin x with the statement A.
Since the zeros of sinx\sin x are at x=nπx = n\pi, and not at nπ2\frac{n \pi}{2}, statement A is false.

STEP 5

Evaluate statement B: The domain of y=cotxy=\cot x is all real numbers except for values of xx for which cosx=0\cos x=0.
The domain of the cotangent function is all real numbers except for the values that make the denominator of cotx=cosxsinx\cot x = \frac{\cos x}{\sin x} zero, which are the values where sinx=0\sin x = 0.

STEP 6

Identify the values of xx for which sinx=0\sin x = 0.
As previously stated, sinx=0\sin x = 0 at x=nπx = n\pi where nn is an integer.

STEP 7

Compare the domain restriction of cotx\cot x with statement B.
Since the domain of y=cotxy=\cot x is restricted by the values of xx where sinx=0\sin x = 0, which are x=nπx = n\pi, statement B is true.

STEP 8

Evaluate statement C: The principal cycle of the graph of y=cotxy=\operatorname{cotx} occurs on the interval (π2,π2)\left(-\frac{\pi}{2}, \frac{\pi}{2}\right).
The cotangent function has a period of π\pi, and its principal cycle occurs where the function is defined and not interrupted by vertical asymptotes. The vertical asymptotes of cotx\cot x occur where sinx=0\sin x = 0, which is at x=nπx = n\pi.

STEP 9

Identify the interval of the principal cycle of y=cotxy=\cot x.
The principal cycle of cotx\cot x is the interval between two consecutive asymptotes, which is (0,π)(0, \pi) or equivalently (π,0)(-\pi, 0). This interval does not match the interval given in statement C.

STEP 10

Compare the principal cycle interval with statement C.
Since the principal cycle of cotx\cot x is not on the interval (π2,π2)\left(-\frac{\pi}{2}, \frac{\pi}{2}\right), statement C is false.

STEP 11

Evaluate statement D: The function y=cotxy=\cot x has infinitely many vertical asymptotes with equations x=nπx=n \pi where nn is an integer.
As previously mentioned, the vertical asymptotes of cotx\cot x occur where sinx=0\sin x = 0, which is at x=nπx = n\pi.

STEP 12

Confirm the presence of vertical asymptotes for y=cotxy=\cot x.
Since cotx\cot x has vertical asymptotes at every integer multiple of π\pi, statement D is true.

STEP 13

Determine the correct statement.
Based on the evaluations, statement B and statement D are true.
The correct answer is B and D.

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