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Question
question 5: standard g.c.2
geometry
in the diagram below, what part of the circle is cd?
a. radius
b. arc
c. diameter
d. chord
question 6: standard g.c.2
the formula $a = \pi r^2$ shows that a circle’s area is related to its _____.
a. chord
b. diameter
c. radius
d. circumference
question 7: standard g.c.2
a central angle is _____ the arc it intercepts.
a. equal to
b. half of the
c. twice as much as
d. complementary to
question 8: standard g.c.2
central angle cab is equal to 114.6 degrees. what is the measure of arc cb?
a. 65.4
b. 114.6
c. 245.5
d. 34.6
question 9: standard g.c.2
geometry
if the measure of arc bc = 42, what is the measure of central angle c
a. 178
b. 138
c. 48
d. 42
use this diagram for questions 10 and 11.
question 10: standard g.c.2
what is the measure of arc bc?
a. 72
b. 18
c. 108
d. 36
question 11: standard g.c.2
what is the measure of inscribed angle cdb?
a. 72
b. 18
c. 108
d. 36
Question 5
To determine what part of the circle \( CD \) is, we recall the definitions:
- Radius: A line from the center to the circumference.
- Arc: A part of the circumference.
- Diameter: A chord passing through the center (longest chord).
- Chord: A line segment with both endpoints on the circle.
From the diagram (a line through the circle with endpoints on the circle), \( CD \) (assuming the line is a diameter - but wait, the options: if the line is a diameter (passes through center) or chord. Wait, the diagram shows a line with two points on the circle, and if it passes through the center, it's diameter. But the options: let's check. Wait, the first diagram: a line with two points on the circle, and the center \( A \). So the line passes through \( A \)? Wait, the diagram: a circle with center \( A \), and a line with two points on the circle, passing through \( A \)? Then \( CD \) (the line) would be a diameter. Wait, but the options: a. Radius, b. Arc, c. Diameter, d. Chord. Wait, a diameter is a chord that passes through the center. So if the line passes through the center, it's diameter. But maybe the diagram: the line is a chord passing through the center, so diameter. But let's re - check. Wait, the question is "what part of the circle is \( CD \)". If \( CD \) is a line with both ends on the circle and passing through the center, it's diameter. But maybe the diagram: the line is a chord (if it doesn't pass through center, but the center is \( A \). Wait, maybe the diagram shows a diameter. But the options: c. Diameter. Wait, but maybe I made a mistake. Wait, no: a diameter is a chord that passes through the center. So if the line passes through the center, it's diameter. So the answer should be c. Diameter? Wait, no, wait the options: let's re - read. The options are a. Radius, b. Arc, c. Diameter, d. Chord. Wait, maybe the diagram is a line with two points on the circle, not passing through the center? No, the center is \( A \), so the line passes through \( A \). So \( CD \) (the line) is a diameter. But wait, maybe the question is mis - drawn. Wait, no, the standard: a diameter is a chord through the center. So the answer is c. Diameter? Wait, no, wait the first option: a. Radius (no, radius is from center to circle), b. Arc (no, it's a line segment), c. Diameter (yes, if it passes through center), d. Chord (a chord is any segment with endpoints on circle; diameter is a type of chord). But the diagram shows a line passing through the center, so it's a diameter. So the correct option is c. Diameter? Wait, no, maybe the diagram is a chord (not passing through center). Wait, the user's diagram: "a circle with center A, and a line with two points on the circle, and the center A is inside the circle, and the line passes through A". So the line is a diameter. So the answer is c. Diameter.
The formula for the area of a circle is \( A=\pi r^{2} \), where \( r \) is the radius. We analyze the options:
- Chord: A line segment with endpoints on the circle, not related to the area formula.
- Diameter: \( d = 2r \), the area formula uses \( r \), not \( d \) directly.
- Radius: The formula \( A=\pi r^{2} \) clearly shows the area is related to the radius \( r \).
- Circumference: The formula for circumference is \( C = 2\pi r \) or \( C=\pi d \), not related to the area formula in the form \( A=\pi r^{2} \).
So the answer is c. Radius.
By the definition of a central angle, a central angle is equal in measure to the arc it intercepts. This is a fundamental concept in circle geometry: the measure of a central angle is equal to the measure of its intercepted arc.
- Option a: Equal to - matches the definition.
- Option b: Half of the - incorrect, inscribed angles are half of the intercepted arc.
- Option c: Twice as much as - incorrect.
- Option d: Complementary to - complementary angles add up to 90 degrees, not related to central angles and arcs.
So the answer is a. Equal to.
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c. Diameter