AnswersPrecalculusPowers and Roots of Complex Numbers

Powers and Roots of Complex Numbers — Unit test Answers

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1
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An isosceles triangle’s altitude will bisect its base. Which expression could be used to find the area of the isosceles triangle above?

Question illustration
A
StartFraction start root 40 end root . start root 40 end root over 2 EndFraction
Option A
B
StartFraction start root 40 end root . start root 68 end root over 2 EndFraction
Option B
C
StartFraction start root 232 end root . start root 288 end root over 2 EndFraction
Option C
D
StartFraction start root 232 end root . start root 164 end root over 2 EndFraction
Option D
2
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For two complex numbers z and w, which diagram shows the geometric representation of zw?

A
On a coordinate plane, the y-axis is labeled imaginary and the x-axis is labeled real. A line with length r 1 goes to point z, a line with length r 1 + r 2 goes to point z w, and a line with length r 2 goes to point w. The angle to line w is theta 2, z is theta 1, z w is theta 1 minus theta 2.
Option A
B
On a coordinate plane, the y-axis is labeled imaginary and the x-axis is labeled real. A line with length r 1 goes to point z, a line with length r 1 r 2 goes to point z w, and a line with length r 2 goes to point w. The angle to line w is theta 2, z is theta 1, z w is theta 1 minus theta 2.
Option B
C
On a coordinate plane, the y-axis is labeled imaginary and the x-axis is labeled real. A line with length r 1 + r 2 goes to point z w, a line with length r 1 goes to point z, and a line with length r 2 goes to point w. The angle to line w is theta 2, z is theta 1, z w is theta 1 + theta 2.
Option C
D
On a coordinate plane, the y-axis is labeled imaginary and the x-axis is labeled real. A line with length r 1 r 2 goes to point z w, a line with length r 1 goes to point z, and a line with length r 2 goes to point w. The angle to line w is theta 2, z is theta 1, z w is theta 1 + theta 2.
Option D
3

What are the conjugate and modulus of –14 – 2i?

A
14 + 2i and
Option A
B
14 + 2i and
Option B
C
–14 + 2i and
Option C
D
–14 + 2i and
Option D
4

Review the graph of complex number z.

Question illustration
A
(cos(135°) + isin(135°))
Option A
B
(cos(135°) + isin(135°))
Option B
C
(cos(225°) + isin(225°))
Option C
D
(cos(225°) + isin(225°))
Option D
5

Consider the polar curve r = 4sin(2θ). What is the length of each petal, and how many petals does the graph have?

A
The length of each petal is 2, and the number of petals is 2.
B
The length of each petal is 2, and the number of petals is 4.
C
The length of each petal is 4, and the number of petals is 2.
D
The length of each petal is 4, and the number of petals is 4.
6

Which phrase describes how to divide a complex number z by r(cos θ + i sin θ)?

A
Scale by a factor of and rotate clockwise by θ.
Option A
B
Scale by a factor of r and rotate clockwise by θ.
C
Scale by a factor of and rotate counterclockwise by θ.
Option C
D
Scale by a factor of r and rotate counterclockwise by θ.
7

Review the graph.

Question illustration
A
quadrant I
B
quadrant II
C
quadrant III
D
quadrant IV
9

What is the quotient of ?

Question illustration
A
45 (cosine (StartFraction pi Over 3 EndFraction) + I sine (StartFraction pi Over 3 EndFraction) )
Option A
B
88 (cosine (StartFraction pi Over 3 EndFraction) + I sine (StartFraction pi Over 3 EndFraction) )
Option B
C
45 (cosine (StartFraction pi Over 6 EndFraction) + I sine (StartFraction pi Over 6 EndFraction) )
Option C
D
88 (cosine (StartFraction pi Over 6 EndFraction) + I sine (StartFraction pi Over 6 EndFraction) )
Option D
10

The following statements are about finding a midpoint of a segment in the complex plane. Which statement is false?

A
The midpoint is the average of the endpoints.
B
First add the endpoints and then multiply by 1/2.
C
First subtract the endpoints and then divide by 2.
D
The midpoint of complex conjugates will lie on the x-axis.
13

Which equation represents the rectangular form of r = 8?

A
x2 + y2 = 16
B
x2 + y2 = 64
C
StartRoot x squared + y squared EndRoot = 16
Option C
D
StartRoot x squared + y squared EndRoot = 64
Option D
14

Which region on the unit circle contains a cube root of – 8 – 8i?

A
in quadrant I
B
in quadrant II
C
on the imaginary axis
D
on the real axis

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