High School Math : Understanding Radians and Conversions

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Understanding Radians And Conversions

What is the value of the angle \displaystyle \frac{3\pi}{2} radians when converted to degrees?

Possible Answers:

\displaystyle 270

\displaystyle -180

\displaystyle 90

\displaystyle -45

\displaystyle 135

Correct answer:

\displaystyle 270

Explanation:

The answer can be found using the conversion of 1 radian equals \displaystyle \frac{180}{\pi} degrees.  Multiplying \displaystyle \frac{3\pi}{2} by this conversion factor gives 270 degrees.

Example Question #11 : The Unit Circle And Radians

A point has Cartesian coordinates \displaystyle (1,3). Rewrite this as an ordered pair in the polar coordinate plane, rounding the coordinates to the nearest hundredth.

Possible Answers:

\displaystyle (2.83, 0.32)

\displaystyle (3.16,0.32)

\displaystyle (3.16,0.80)

\displaystyle (2.83, 1.25)

\displaystyle (3.16,1.25)

Correct answer:

\displaystyle (3.16,1.25)

Explanation:

Set \displaystyle x=1, y=3. Calculate the polar coordinates \displaystyle (r,\theta ) as follows:

\displaystyle r = \sqrt{x^{2}+y^{2}}= \sqrt{1^{2}+3^{2}}=\sqrt{10} \approx 3.16

\displaystyle \theta = \arctan \frac{y}{x}= \arctan \frac{3}{1} = \arctan 3 \approx 1.25

Example Question #34 : Trigonometry

How many degrees are in \displaystyle \frac{\pi}{6} radians?

Possible Answers:

\displaystyle 45^\circ

\displaystyle 120^\circ

\displaystyle 360^\circ

\displaystyle 30^\circ

\displaystyle 60^\circ

Correct answer:

\displaystyle 30^\circ

Explanation:

\displaystyle \frac{x^\circ}{\frac{\pi}{6}}=\frac{180^\circ}{\pi}

Cross multiply:

\displaystyle x^\circ*\pi=180^\circ*\frac{\pi}{6}

Notice that the \displaystyle \pi's cancel out:

\displaystyle x^\circ=180^\circ*\frac{1}{6}

\displaystyle x^\circ=30^\circ

Example Question #2 : Understanding Radians And Conversions

How many radians are in \displaystyle 180^\circ?

Possible Answers:

\displaystyle 4\pi

\displaystyle \frac{\pi}{2}

\displaystyle 2\pi

\displaystyle \pi

\displaystyle 3\pi

Correct answer:

\displaystyle \pi

Explanation:

The relationship between degrees and radians is \displaystyle 180^\circ=\pi radians. Therefore, \displaystyle 180^\circ would be \displaystyle \pi radians.

Example Question #3 : Understanding Radians And Conversions

Express in radians: \displaystyle 125^{\circ }

Possible Answers:

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

\displaystyle \frac{11\pi }{18}

\displaystyle \frac{15\pi }{36}

\displaystyle \frac{25\pi }{36}

\displaystyle \frac{5\pi }{9}

Correct answer:

\displaystyle \frac{25\pi }{36}

Explanation:

Since \displaystyle 180 ^{\circ } = \pi \textrm{ rad}, we can convert as follows:

\displaystyle 125 \cdot \frac{\pi }{180} = \frac{25\pi }{36}

Example Question #1 : Understanding Radians And Conversions

How many radians are in \displaystyle 85^\circ?

Possible Answers:

\displaystyle \frac{36}{17}\pi

\displaystyle \frac{3}{5}\pi

\displaystyle \frac{17}{36}\pi

\displaystyle \frac{9}{4}\pi

\displaystyle \frac{4}{9}\pi

Correct answer:

\displaystyle \frac{17}{36}\pi

Explanation:

Since there are \displaystyle \pi radians for every \displaystyle 180^\circ, we can set up a proportion to solve.

\displaystyle \frac{85^\circ}{x}=\frac{180^\circ}{\pi}

Cross multiply.

\displaystyle 85^\circ*\pi=180^\circ *x

Divide both sides by \displaystyle 180^\circ.

\displaystyle \frac{85^\circ}{180^\circ}*\pi=x

\displaystyle \frac{17}{36}\pi=x

Example Question #2 : Understanding Radians And Conversions

How many radians are in \displaystyle 270^\circ?

Possible Answers:

\displaystyle 2\pi

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

\displaystyle \pi

\displaystyle \frac{5\pi}{2}

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

Correct answer:

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

Explanation:

The conversion for radians is \displaystyle 180^\circ=\pi, so we can make a ratio:

\displaystyle \frac{270^\circ}{x}=\frac{180^\circ}{\pi}

Cross multiply:

\displaystyle 270^\circ*\pi=180^\circ*x

Isolate \displaystyle x:

\displaystyle \frac{270^\circ}{180^\circ}\pi=x

\displaystyle \frac{3\pi}{2}=x

Example Question #1 : Understanding Radians And Conversions

How many degrees are in \displaystyle \frac{\pi}{3} radians?

Possible Answers:

\displaystyle 540^\circ

\displaystyle 15^\circ

\displaystyle 45^\circ

\displaystyle 30^\circ

\displaystyle 60^\circ

Correct answer:

\displaystyle 60^\circ

Explanation:

The conversion for radians is \displaystyle 180^\circ=\pi, so we can make a ratio:

\displaystyle \frac{x^\circ}{\frac{\pi}{3}}=\frac{180^\circ}{\pi}

Cross multiply:

\displaystyle x^\circ*\pi=180^\circ*\frac{\pi}{3}

Divide both sides by \displaystyle \pi:

\displaystyle x^\circ=\frac{180^\circ}{3}

\displaystyle x^\circ=60^\circ

Example Question #1771 : High School Math

How many degrees are in \displaystyle \frac{8\pi}{3} radians?

Possible Answers:

\displaystyle 420^\circ

\displaystyle 460^\circ

\displaystyle 480^\circ

\displaystyle 120^\circ

\displaystyle 30^\circ

Correct answer:

\displaystyle 480^\circ

Explanation:

The conversion for radians is \displaystyle 180^\circ=\pi, so we can make a ratio:

\displaystyle \frac{x^\circ}{\frac{8\pi}{3}}=\frac{180^\circ}{\pi}

Cross multiply:

\displaystyle x^\circ*\pi=180^\circ*\frac{8\pi}{3}

Notice that the \displaystyle \pi's cancel out:

\displaystyle x^\circ=180^\circ*\frac{8}{3}

\displaystyle x^\circ=480^\circ

 

Example Question #2 : Understanding Radians And Conversions

How many degrees are in \displaystyle \frac{3\pi}{4} radians?

Possible Answers:

\displaystyle 405^\circ

\displaystyle 135^\circ

\displaystyle 225^\circ

\displaystyle 180^\circ

\displaystyle 45^\circ

Correct answer:

\displaystyle 135^\circ

Explanation:

The conversion for radians is \displaystyle 180^\circ=\pi, so we can make a ratio:

\displaystyle \frac{x^\circ}{\frac{3\pi}{4}}=\frac{180^\circ}{\pi}

Cross multiply:

\displaystyle x^\circ*\pi=180^\circ*\frac{3\pi}{4}

Notice that the \displaystyle \pi's cancel out:

\displaystyle x^\circ=180^\circ*\frac{3}{4}

\displaystyle x^\circ=135^\circ

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