New SAT Math - Calculator : Circles

Study concepts, example questions & explanations for New SAT Math - Calculator

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Example Questions

Example Question #35 : Unit Circle And Radians

Simplify and give the followoing expression in degrees:

 

\(\displaystyle 2\pi-\frac{\pi}{4}\)

Possible Answers:

\(\displaystyle 285^{\circ}\)

\(\displaystyle 270^{\circ}\)

\(\displaystyle 300^{\circ}\)

\(\displaystyle 325^{\circ}\)

\(\displaystyle 315^{\circ}\)

Correct answer:

\(\displaystyle 315^{\circ}\)

Explanation:

First we need to simplify the expression:

 

\(\displaystyle 2\pi-\frac{\pi}{4}=\frac{8\pi-\pi}{4}=\frac{7\pi}{4}\)

Then multiply  by \(\displaystyle \frac{180^{\circ}}{\pi}\):

 

\(\displaystyle \frac{7\pi}{4}\times \frac{180^{\circ}}{\pi}=\frac{7\times 180^{\circ}}{4}=315^{\circ}\)

Example Question #21 : Circles

Simplify and give the followoing expression in degrees:

 

\(\displaystyle \frac{\frac{2\pi}{7}+\frac{\pi}{14}}{\frac{1}{7}}\)

Possible Answers:

\(\displaystyle 450^{\circ}\)

\(\displaystyle 380^{\circ}\)

\(\displaystyle 350^{\circ}\)

\(\displaystyle 480^{\circ}\)

\(\displaystyle 420^{\circ}\)

Correct answer:

\(\displaystyle 450^{\circ}\)

Explanation:

First we need to simplify the expression:

 

\(\displaystyle \frac{\frac{2\pi}{7}+\frac{\pi}{14}}{\frac{1}{7}}=\frac{\frac{4\pi+\pi}{14}}{\frac{1}{7}}=\frac{5\pi}{2}\)

Then multiply by \(\displaystyle \frac{180^{\circ}}{\pi}\):

 

\(\displaystyle \frac{5\pi}{2}\times \frac{180^{\circ}}{\pi}=\frac{5\times 180^{\circ}}{2}=450^{\circ}\)

Example Question #21 : Radians

Convert \(\displaystyle \frac{2\pi}{3}\) radians to degrees.

Possible Answers:

\(\displaystyle 150^\circ\)

\(\displaystyle 30^\circ\)

\(\displaystyle 60^\circ\)

\(\displaystyle 250^\circ\)

\(\displaystyle 120^\circ\)

Correct answer:

\(\displaystyle 120^\circ\)

Explanation:

Use the conversion \(\displaystyle \pi \textup{ radians}= 180\textup{ degrees}\).

Since we are converting radians to degrees, multiply by 180 degrees and divide by \(\displaystyle \pi\) radians.

\(\displaystyle \frac{2\pi}{3} \textup{ radians}\left(\frac{180 \textup{ degrees}}{\pi\textup{ radian}}\right)= 120\textup{ degrees}\)

Example Question #21 : Circles

How many degrees is 3 radians?

Possible Answers:

\(\displaystyle 150^{\circ}\)

\(\displaystyle 189^{\circ}\)

\(\displaystyle 156^{\circ}\)

None of these other answers.

\(\displaystyle 172^{\circ}\)

Correct answer:

\(\displaystyle 172^{\circ}\)

Explanation:

When going from radians to degrees one multiplies by the conversion factor 

\(\displaystyle \frac{180^{\circ}}{\pi rad}\).

The radians cancel and the answer is left in degrees.

\(\displaystyle 3\hspace{1mm}{\color{Red} rad}\cdot\frac{180^{\circ}}{\pi {\color{Red} rad}}=\frac{540^\circ}{\pi}=172^{\circ}\)

Example Question #22 : Circles

Convert to radians: \(\displaystyle 33^o\)

Possible Answers:

\(\displaystyle 0.183\)

\(\displaystyle 0.189\)

\(\displaystyle 0.058\)

\(\displaystyle 0.576\)

\(\displaystyle 1.736\)

Correct answer:

\(\displaystyle 0.576\)

Explanation:

To convert to radians, set up the ratio \(\displaystyle \frac{180}{\pi } = \frac{33} { x}\):

\(\displaystyle 180 x = 33 \pi\)

\(\displaystyle x = 33 \pi \div 180 \approx 0.576\)

Example Question #23 : Circles

Convert to degrees: \(\displaystyle \frac{2 \pi }{7}\)

Possible Answers:

\(\displaystyle 51.43^o\)

\(\displaystyle 16.37^o\)

\(\displaystyle 0.016^o\)

\(\displaystyle 147.58^o\)

Correct answer:

\(\displaystyle 51.43^o\)

Explanation:

To convert, divide by \(\displaystyle \pi\) and multiply by \(\displaystyle 180\):

\(\displaystyle \frac{2 \pi }{7 } \div \pi = \frac{2}{7}\)

\(\displaystyle \frac{2}{7} \cdot 180 \approx 51.47^o\)

Example Question #26 : Circles

Convert \(\displaystyle \frac{7\pi}{4}\) radians into degrees.

Possible Answers:

\(\displaystyle 225^{\circ}\)

\(\displaystyle 270^{\circ}\)

\(\displaystyle 345^{\circ}\)

\(\displaystyle 285^{\circ}\)

\(\displaystyle 315^{\circ}\)

Correct answer:

\(\displaystyle 315^{\circ}\)

Explanation:

Recall the definition of "radians" derived from the unit circle:

\(\displaystyle 180^{\circ} = \pi rad\)

The quantity of radians given in the problem is \(\displaystyle \frac{7\pi}{4}\). All that is required to convert this measure into degrees is to denote the unknown angle measure in degrees by \(\displaystyle \Theta\) and set up a proportion equation using the aforementioned definition relating radians to degrees:

\(\displaystyle \frac{180^{\circ}}{\Theta} = \frac{\pi rad}{\frac{7\pi}{4} rad}\)

Cross-multiply the denominators in these fractions to obtain:

\(\displaystyle 1260^{\circ}\pi rad=4\Theta\pi rad\)

or

\(\displaystyle 315^{\circ}\pi rad =\Theta\pi rad\).

Canceling like terms in these equations yields

\(\displaystyle \Theta = 315^{\circ}\)

Hence, the correct angle measure of \(\displaystyle \frac{7\pi}{4}\) in degrees is \(\displaystyle 315^{\circ}\).

Example Question #24 : Circles

\(\displaystyle \frac{37\pi}{18}\) radians is equivalent to how many degrees?

Possible Answers:

\(\displaystyle 10^\circ\)

\(\displaystyle 370^\circ\)

\(\displaystyle 185^\circ\)

\(\displaystyle 350^\circ\)

Correct answer:

\(\displaystyle 370^\circ\)

Explanation:

1 radian is equal to \(\displaystyle \frac{180}{\pi}\) degrees. Using this conversion factor,

\(\displaystyle \frac{37\pi}{18}\times\frac{180}{\pi}=37\times10=370\).

Example Question #24 : Radians And Conversions

Convert \(\displaystyle 150^{\circ}\) into radians. 

Possible Answers:

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

\(\displaystyle \frac{5\pi}{6}\)

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

\(\displaystyle \frac{10\pi}{6}\)

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

Correct answer:

\(\displaystyle \frac{5\pi}{6}\)

Explanation:

Recall that there are 360 degrees in a circle which is equivalent to \(\displaystyle 2\pi\) radians. In order to convert between radians and degrees use the relationship that,

\(\displaystyle 360^\circ=2\pi \Rightarrow 180^\circ=\pi\)

Thus, in order to convert from degrees to radians you need to multiply by \(\displaystyle \frac{\pi}{180}\).

So in this particular case, 

\(\displaystyle 150*\frac{\pi}{180}=\frac{5\pi}{6}\).

Example Question #23 : Radians

Convert \(\displaystyle 330^{\circ}\) into radians.

Possible Answers:

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

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

\(\displaystyle \frac{5\pi}{6}\)

\(\displaystyle \frac{7\pi}{5}\)

\(\displaystyle \frac{7\pi}{3}\)

Correct answer:

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

Explanation:

Recall that there are 360 degrees in a circle which is equivalent to  radians. In order to convert between radians and degrees use the relationship that, \(\displaystyle 360^\circ=2\pi \Rightarrow 180^\circ=\pi\)

Thus, in order to convert from degrees to radians you need to multiply by . \(\displaystyle \frac{\pi}{180}\)

So in this particular case,

 \(\displaystyle 330*\frac{\pi}{180}=\frac{11\pi}{6}\).

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