Intermediate Geometry : Circles

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #81 : Plane Geometry

The radius of a circle is \(\displaystyle 8\). Find the length of an arc if it has a measure of \(\displaystyle 60\) degrees.

Possible Answers:

\(\displaystyle \frac{4}{3}\pi\)

\(\displaystyle \frac{2}{3}\pi\)

\(\displaystyle \frac{8}{3}\pi\)

\(\displaystyle 2\pi\)

Correct answer:

\(\displaystyle \frac{2}{3}\pi\)

Explanation:

Recall that the length of an arc is merely a part of the circle's circumference.

We can then write the following equation to find the length of an arc:

\(\displaystyle \text{Arc Length}=\frac{\text{Arc angle measure}}{360}\times2\pi\times \text{radius}\)

Plug in the values of the arc angle measure and the radius to find the length of the arc.

\(\displaystyle \text{Arc Length}=\frac{60}{360}\times 2\pi\times 8=\frac{2}{3}\pi\)

Example Question #81 : Sectors

The radius of a circle is \(\displaystyle 9\). Find the length of an arc if it has a measure of \(\displaystyle 200\) degrees.

Possible Answers:

\(\displaystyle 9\pi\)

\(\displaystyle 12\pi\)

\(\displaystyle 10\pi\)

\(\displaystyle 15\pi\)

Correct answer:

\(\displaystyle 10\pi\)

Explanation:

Recall that the length of an arc is merely a part of the circle's circumference.

We can then write the following equation to find the length of an arc:

\(\displaystyle \text{Arc Length}=\frac{\text{Arc angle measure}}{360}\times2\pi\times \text{radius}\)

Plug in the values of the arc angle measure and the radius to find the length of the arc.

\(\displaystyle \text{Arc Length}=\frac{200}{360}\times 2\pi\times 9=10\pi\)

Example Question #81 : Intermediate Geometry

The radius of a circle is \(\displaystyle 10\). Find the length of an arc if it has a measure of \(\displaystyle 40\) degrees.

Possible Answers:

\(\displaystyle \frac{20}{9}\pi\)

\(\displaystyle \frac{2}{9}\pi\)

\(\displaystyle \frac{22}{9}\pi\)

\(\displaystyle \frac{25}{9}\pi\)

Correct answer:

\(\displaystyle \frac{20}{9}\pi\)

Explanation:

Recall that the length of an arc is merely a part of the circle's circumference.

We can then write the following equation to find the length of an arc:

\(\displaystyle \text{Arc Length}=\frac{\text{Arc angle measure}}{360}\times2\pi\times \text{radius}\)

Plug in the values of the arc angle measure and the radius to find the length of the arc.

\(\displaystyle \text{Arc Length}=\frac{40}{360}\times 2\pi\times 10=\frac{20}{9}\pi\)

Example Question #84 : Plane Geometry

The radius of a circle is \(\displaystyle 12\). Find the length of an arc if it has a measure of \(\displaystyle 130\) degrees.

Possible Answers:

\(\displaystyle \frac{26}{3}\pi\)

\(\displaystyle \frac{22}{3}\pi\)

\(\displaystyle 9\pi\)

\(\displaystyle 8\pi\)

Correct answer:

\(\displaystyle \frac{26}{3}\pi\)

Explanation:

Recall that the length of an arc is merely a part of the circle's circumference.

We can then write the following equation to find the length of an arc:

\(\displaystyle \text{Arc Length}=\frac{\text{Arc angle measure}}{360}\times2\pi\times \text{radius}\)

Plug in the values of the arc angle measure and the radius to find the length of the arc.

\(\displaystyle \text{Arc Length}=\frac{130}{360}\times 2\pi\times 12=\frac{26}{3}\pi\)

Example Question #81 : Sectors

The radius of a circle is \(\displaystyle 12\). Find the length of an arc if it has a measure of \(\displaystyle 180\) degrees.

Possible Answers:

\(\displaystyle 12\pi\)

\(\displaystyle 24\pi\)

\(\displaystyle 30\pi\)

\(\displaystyle 18\pi\)

Correct answer:

\(\displaystyle 12\pi\)

Explanation:

Recall that the length of an arc is merely a part of the circle's circumference.

We can then write the following equation to find the length of an arc:

\(\displaystyle \text{Arc Length}=\frac{\text{Arc angle measure}}{360}\times2\pi\times \text{radius}\)

Plug in the values of the arc angle measure and the radius to find the length of the arc.

\(\displaystyle \text{Arc Length}=\frac{180}{360}\times 2\pi\times 12=12\pi\)

Example Question #81 : Intermediate Geometry

The radius of a circle is \(\displaystyle 1\). Find the length of an arc if it has a measure of \(\displaystyle 210\) degrees.

Possible Answers:

\(\displaystyle \frac{4}{3}\pi\)

\(\displaystyle \frac{7}{6}\pi\)

\(\displaystyle \frac{11}{6}\pi\)

\(\displaystyle \frac{13}{6}\pi\)

Correct answer:

\(\displaystyle \frac{7}{6}\pi\)

Explanation:

Recall that the length of an arc is merely a part of the circle's circumference.

We can then write the following equation to find the length of an arc:

\(\displaystyle \text{Arc Length}=\frac{\text{Arc angle measure}}{360}\times2\pi\times \text{radius}\)

Plug in the values of the arc angle measure and the radius to find the length of the arc.

\(\displaystyle \text{Arc Length}=\frac{210}{360}\times 2\pi\times 1=\frac{7}{6}\pi\)

Example Question #87 : Plane Geometry

Find the length of the arc if the radius of a circle is \(\displaystyle 12\) and the measure of the central angle is \(\displaystyle 55\) degrees.

Possible Answers:

\(\displaystyle \frac{11}{3}\pi\)

\(\displaystyle 5\pi\)

\(\displaystyle 4\pi\)

\(\displaystyle \frac{13}{3}\pi\)

Correct answer:

\(\displaystyle \frac{11}{3}\pi\)

Explanation:

An arc is just a piece—or a fraction—of a circle's circumference. Use the following formula to find the length of an arc:

\(\displaystyle \text{Length of Arc}=\frac{\text{Measure of central angle}}{360}\times2\pi\times \text{radius}\)

Substitute in the given values for the central angle and the radius.

\(\displaystyle \text{Length of Arc}=\frac{55}{360}\times 2\pi \times 12\)

Solve.

\(\displaystyle \text{Length of Arc}=\frac{11}{3}\pi\)

Example Question #88 : Plane Geometry

Find the length of an arc if the radius of the circle is \(\displaystyle 13\) and the measurement of the central angle is \(\displaystyle 65\) degrees.

Possible Answers:

\(\displaystyle \frac{169}{36}\pi\)

\(\displaystyle \frac{19}{4}\pi\)

\(\displaystyle \frac{37}{6}\pi\)

\(\displaystyle \frac{110}{7}\pi\)

Correct answer:

\(\displaystyle \frac{169}{36}\pi\)

Explanation:

An arc is just a piece—or a fraction—of a circle's circumference. Use the following formula to find the length of an arc:

\(\displaystyle \text{Length of Arc}=\frac{\text{Measure of central angle}}{360}\times2\pi\times \text{radius}\)

Substitute in the given values for the central angle and the radius.

\(\displaystyle \text{Length of Arc}=\frac{65}{360}\times 2\pi \times 13\)

Solve.

\(\displaystyle \text{Length of Arc}=\frac{169}{36}\pi\)

Example Question #81 : Sectors

Find the length of an arc if the radius of the circle is \(\displaystyle 14\) and the measurement of the central angle is \(\displaystyle 75\) degrees.

Possible Answers:

\(\displaystyle \frac{13}{3}\pi\)

\(\displaystyle 8\pi\)

\(\displaystyle \frac{25}{6}\pi\)

\(\displaystyle \frac{35}{6}\pi\)

Correct answer:

\(\displaystyle \frac{35}{6}\pi\)

Explanation:

An arc is just a piece—or a fraction—of a circle's circumference. Use the following formula to find the length of an arc:

\(\displaystyle \text{Length of Arc}=\frac{\text{Measure of central angle}}{360}\times2\pi\times \text{radius}\)

Substitute in the given values for the central angle and the radius.

\(\displaystyle \text{Length of Arc}=\frac{75}{360}\times 2\pi \times 14\)

Solve.

\(\displaystyle \text{Length of Arc}=\frac{35}{6}\pi\)

Example Question #81 : Plane Geometry

Find the length of an arc if the radius of the circle is \(\displaystyle 15\) and the measurement of the central angle is \(\displaystyle 80\) degrees.

Possible Answers:

\(\displaystyle \frac{20}{3}\pi\)

\(\displaystyle \frac{29}{3}\pi\)

\(\displaystyle \frac{22}{3}\pi\)

\(\displaystyle 6\pi\)

Correct answer:

\(\displaystyle \frac{20}{3}\pi\)

Explanation:

An arc is just a piece—or a fraction—of a circle's circumference. Use the following formula to find the length of an arc:

\(\displaystyle \text{Length of Arc}=\frac{\text{Measure of central angle}}{360}\times2\pi\times \text{radius}\)

Substitute in the given values for the central angle and the radius.

\(\displaystyle \text{Length of Arc}=\frac{80}{360}\times 2\pi \times 15\)

Solve.

\(\displaystyle \text{Length of Arc}=\frac{20}{3}\pi\)

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