MathIsimple

Circle Essentials

Explore the geometry of circles: radius, diameter, circumference, area, sectors, arcs, and tangent lines.

Geometry
Beginner
~45 min
Circle Calculator
Calculate radius, diameter, circumference, and area
1. What is a Circle?

A circle is the set of all points in a plane that are at a fixed distance (the radius) from a fixed point (the center).

Radius (r)

Distance from center to any point on the circle.

Diameter (d)

Distance across the circle through the center. d=2rd = 2r

Chord

A line segment connecting two points on the circle.

Arc

A portion of the circumference (curved part of the circle).

Sector

A "pizza slice" region bounded by two radii and an arc.

Segment

Region between a chord and its arc.

2. Circumference
3. Area
4. Sectors and Arcs
5. Tangent Lines

Practice Quiz

Practice Quiz
20
Questions
0
Correct
0%
Accuracy
1
What is the formula for the circumference of a circle?
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2
What is the formula for the area of a circle?
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3
If the radius of a circle is 5, what is its diameter?
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4
A chord that passes through the center is called:
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5
The distance from the center to any point on the circle is:
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6
What is π\pi approximately equal to?
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7
If the diameter is 14, what is the circumference? (Use π≈227\pi \approx \frac{22}{7})
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8
If the radius is 7, what is the area? (Use π≈227\pi \approx \frac{22}{7})
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9
A line that touches the circle at exactly one point is called:
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10
A tangent line is ___ to the radius at the point of contact.
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11
The area of a semicircle with radius rr is:
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12
The angle in a semicircle (inscribed angle on diameter) is:
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13
What is an arc?
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14
A sector is like a:
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15
The arc length formula for angle θ\theta (in radians) is:
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16
The area of a sector with central angle θ\theta (in radians) is:
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17
If a circle has circumference 20π20\pi, what is its radius?
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18
If a circle has area 49π49\pi, what is its radius?
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19
Two circles with the same center are called:
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20
A central angle of 60°60° subtends what fraction of the circle?
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