Model Real-World Periodic Behavior With Cotangent Quiz

1) Which equation matches Graph A in the figure?

Y = tan(x)

Y = cot(x)

Y = cot(2x)

Y = 2cot(x)

Step 1: Graph A shows a curve decreasing from left to right with vertical asymptotes one unit apart (period π). Step 2: That’s the behavior of the basic cotangent graph. So, the final answer is y = cot(x).

Explanation

Step 1: Graph A shows a curve decreasing from left to right with vertical asymptotes one unit apart (period π). Step 2: That’s the behavior of the basic cotangent graph. So, the final answer is y = cot(x).

2) Which graph in the figure has period π/2?

Graph A

Graph B

Graph C

Graph D

Step 1: The cotangent function’s period = π/b. Step 2: Period π/2 ⇒ b = 2, meaning y = cot(2x). Step 3: Graph C shows more frequent asymptotes (half the normal spacing). So, the final answer is Graph C.

Explanation

Step 1: The cotangent function’s period = π/b. Step 2: Period π/2 ⇒ b = 2, meaning y = cot(2x). Step 3: Graph C shows more frequent asymptotes (half the normal spacing). So, the final answer is Graph C.

3) Which graph in the figure has a vertical asymptote at x = 1?

Graph A

Graph B

Graph C

Graph D

Step 1: A vertical asymptote at x = 1 means the function is shifted horizontally. Step 2: The standard cotangent has asymptotes at x = nπ. Step 3: Shifting by 1 unit moves the asymptote to x = 1. So, the final answer is Graph D.

Explanation

Step 1: A vertical asymptote at x = 1 means the function is shifted horizontally. Step 2: The standard cotangent has asymptotes at x = nπ. Step 3: Shifting by 1 unit moves the asymptote to x = 1. So, the final answer is Graph D.

4) Consider y = a·cot(bx − c) + d with a > 0. Increasing b primarily:

Decreases amplitude

Increases vertical shift

Decreases the period

Increases the period

Step 1: Period = π/b. Step 2: Increasing b makes π/b smaller, reducing the period. So, the final answer is decreases the period.

Explanation

Step 1: Period = π/b. Step 2: Increasing b makes π/b smaller, reducing the period. So, the final answer is decreases the period.

5) Which transformation shifts the cotangent graph π/4 units to the right?

Y = cot(x + π/4)

Y = cot(x − π/4)

Y = cot(2x)

Y = 2cot(x)

Step 1: The term (x − π/4) moves the graph right by π/4. So, the final answer is y = cot(x − π/4).

Explanation

Step 1: The term (x − π/4) moves the graph right by π/4. So, the final answer is y = cot(x − π/4).

6) A signal has intensity modeled by y = 3cot(2x). What is its period?

2π

π

π/2

π/3

Step 1: Period = π/b = π/2 when b = 2. So, the final answer is π/2.

Explanation

Step 1: Period = π/b = π/2 when b = 2. So, the final answer is π/2.

7) Which equation represents a cotangent function that has the same period and vertical scale as y = cot(x) but is shifted upward by 2 units?

Y = 2cot(x)

Y = cot(2x)

Y = cot(x − π/4)

Y = cot(x) + 2

Step 1: Adding “+2” shifts the graph vertically up by 2 units. So, the final answer is y = cot(x) + 2.

Explanation

Step 1: Adding “+2” shifts the graph vertically up by 2 units. So, the final answer is y = cot(x) + 2.

8) The graph of y = cot(x − π/4) will have a vertical asymptote at:

X = −π/4

X = π/4

X = π/2

X = 3π/4

Step 1: cot(x − π/4) = undefined when x − π/4 = 0 ⇒ x = π/4. So, the final answer is x = π/4.

Explanation

Step 1: cot(x − π/4) = undefined when x − π/4 = 0 ⇒ x = π/4. So, the final answer is x = π/4.

9) If y = −cot(x), compared to y = cot(x) it is:

Reflected across the x-axis

Shifted left by π/2

Reflected across the y-axis

Stretched vertically by 2

The negative sign causes reflection across the x-axis. So, the final answer is reflected across the x-axis.

Explanation

The negative sign causes reflection across the x-axis. So, the final answer is reflected across the x-axis.

10) Which function has the same period as y = cot(3x)?

Y = cot(x/3)

Y = cot(6x)

Y = cot(x)

Y = cot(3x) + 5

Step 1: Adding 5 shifts vertically but does not affect period. Step 2: Period depends only on b (here, b = 3). So, the final answer is y = cot(3x) + 5.

Explanation

Step 1: Adding 5 shifts vertically but does not affect period. Step 2: Period depends only on b (here, b = 3). So, the final answer is y = cot(3x) + 5.

11) A rotating beacon’s angular position is modeled by y = cot(ωt). Doubling ω will:

Double the amplitude

Halve the period

Double the period

Shift the graph right

Step 1: Period = π/ω. Step 2: Doubling ω halves the period. So, the final answer is halve the period.

Explanation

Step 1: Period = π/ω. Step 2: Doubling ω halves the period. So, the final answer is halve the period.

12) For y = a·cot(bx), the distance between consecutive vertical asymptotes equals:

2π/a

2π/b

π/a

π/b

Step 1: The spacing between asymptotes equals the period, π/b. So, the final answer is π/b.

Explanation

Step 1: The spacing between asymptotes equals the period, π/b. So, the final answer is π/b.

13) Which equation produces a vertical stretch compared to y = cot(x)?

Y = 3cot(x)

Y = cot(3x)

Y = cot(x) + 3

Y = cot(x − 3)

Multiplying by 3 increases the vertical scale (stretch). So, the final answer is y = 3cot(x).

Explanation

Multiplying by 3 increases the vertical scale (stretch). So, the final answer is y = 3cot(x).

14) On [0, π], y = cot(2x) has vertical asymptotes at:

X = 0, π/2, π

X = 0, π

X = π/4, 3π/4

X = π/2 only

Step 1: For y = cot(2x), asymptotes occur where sin(2x) = 0. Step 2: 2x = 0, π, 2π ⇒ x = 0, π/2, π. So, the final answer is x = 0, π/2, π.

Explanation

Step 1: For y = cot(2x), asymptotes occur where sin(2x) = 0. Step 2: 2x = 0, π, 2π ⇒ x = 0, π/2, π. So, the final answer is x = 0, π/2, π.

15) The phase shift of y = cot(2x − π/2) is:

Left π/4

Right π/4

Right π/2

Left π/2

Phase shift = c/b = (π/2)/2 = π/4 to the right. So, the final answer is right π/4.

Explanation

Phase shift = c/b = (π/2)/2 = π/4 to the right. So, the final answer is right π/4.

16) Which statement about cotangent is true?

Y = cot(x) is even

Y = cot(x) has period 2π

Y = cot(x) is odd

Y = cot(x) has amplitude 1

cot(−x) = −cot(x) ⇒ function is odd. So, the final answer is cot(x) is odd.

Explanation

cot(−x) = −cot(x) ⇒ function is odd. So, the final answer is cot(x) is odd.

17) A model y = 4 + cot(x) best describes which transformation?

Horizontal shift right 4

Horizontal stretch by 4

Vertical stretch by 4

Vertical shift up 4

The +4 outside moves the graph up by 4 units. So, the final answer is vertical shift up 4.

Explanation

The +4 outside moves the graph up by 4 units. So, the final answer is vertical shift up 4.

18) Which graph shows a horizontal compression relative to y = cot(x)?

Y = 2cot(x)

Y = cot(x − π/4)

Y = cot(2x)

Y = cot(x/2)

Step 1: b = 2 compresses horizontally (smaller period). So, the final answer is y = cot(2x).

Explanation

Step 1: b = 2 compresses horizontally (smaller period). So, the final answer is y = cot(2x).

19) The zeros of y = cot(x − π/4) in [0, 2π] occur at:

X = π/4, 5π/4

X = 0, π

X = π/2, 3π/2

X = −π/4, 3π/4

Step 1: Zeros occur when cos(x − π/4) = 0 ⇒ x − π/4 = π/2 + nπ ⇒ x = π/4 + π/2 + nπ. Step 2: Within [0, 2π], these are π/4 and 5π/4. So, the final answer is x = π/4, 5π/4.

Explanation

Step 1: Zeros occur when cos(x − π/4) = 0 ⇒ x − π/4 = π/2 + nπ ⇒ x = π/4 + π/2 + nπ. Step 2: Within [0, 2π], these are π/4 and 5π/4. So, the final answer is x = π/4, 5π/4.