High School Math : Angles

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Angles

Solve for \(\displaystyle x\) and \(\displaystyle y\).

Question_3

(Figure not drawn to scale).

Possible Answers:

\(\displaystyle \small x=15^o;\ y=7.5^o\)

\(\displaystyle \small x=7.5^o;\ y=18.75^o\)

\(\displaystyle \small x=15^o;\ y=37.5^o\)

\(\displaystyle \small x=15^o;\ y=52.5^o\)

Correct answer:

\(\displaystyle \small x=15^o;\ y=37.5^o\)

Explanation:

The angles containing the variable \(\displaystyle x\) all reside along one line, therefore, their sum must be \(\displaystyle 180^o\).

\(\displaystyle \small 5x+4x+3x=180^o\)

\(\displaystyle \small 12x=180^o\)

\(\displaystyle \small x=15^o\)

Because \(\displaystyle 2y\) and \(\displaystyle 5x\) are opposite angles, they must be equal.

\(\displaystyle \small 2y=5x\)

\(\displaystyle \small x=15^o\)

\(\displaystyle \small 2y=5(15^o)=75^o\)

\(\displaystyle \small y=\frac{75^o}{2}=37.5^o\)

Example Question #1 : Understanding Complementary And Suplmentary Angles

Are \(\displaystyle 73^{\circ}\) and \(\displaystyle 17^{\circ}\) complementary angles?

Possible Answers:

Yes

Maybe

Not enough information

No

Correct answer:

Yes

Explanation:

Complementary angles add up to \(\displaystyle 90^{\circ}\). Therefore, these angles are complementary.

Example Question #2 : Angles

What angle is complementary to \(\displaystyle 34^\circ\)?

Possible Answers:

\(\displaystyle 56^\circ\)

\(\displaystyle 156^\circ\)

\(\displaystyle 34^\circ\)

\(\displaystyle 66^\circ\)

\(\displaystyle 146^\circ\)

Correct answer:

\(\displaystyle 56^\circ\)

Explanation:

Two complementary angles add up to \(\displaystyle 90^\circ\).

Therefore, \(\displaystyle 34^\circ+x^\circ=90^\circ\).

\(\displaystyle x^\circ=90^\circ-34^\circ\)

\(\displaystyle x^\circ=56^\circ\)

Example Question #3 : Angles

Which of the following angles is supplementary to \(\displaystyle 15^\circ\)?

Possible Answers:

\(\displaystyle 12^\circ\)

\(\displaystyle 75^\circ\)

\(\displaystyle 85^\circ\)

\(\displaystyle 175^\circ\)

\(\displaystyle 165^\circ\)

Correct answer:

\(\displaystyle 165^\circ\)

Explanation:

When two angles are supplementary, they add up to \(\displaystyle 180^\circ\).

For this problem, we can set up an equation and solve for the supplementary angle:

\(\displaystyle x^\circ+15^\circ=180^\circ\)

\(\displaystyle x^\circ=180^\circ-15^\circ\)

\(\displaystyle x^\circ=165^\circ\)

Example Question #4 : Angles

What angle is supplementary to \(\displaystyle 131^\circ\)?

Possible Answers:

\(\displaystyle 41^\circ\)

\(\displaystyle 229^\circ\)

\(\displaystyle 49^\circ\)

\(\displaystyle 140^\circ\)

\(\displaystyle -41^\circ\)

Correct answer:

\(\displaystyle 49^\circ\)

Explanation:

Supplementary angles add up to \(\displaystyle 180^\circ\). That means:

\(\displaystyle x+131^\circ=180^\circ\)

\(\displaystyle x=180^\circ-131^\circ\)

\(\displaystyle x=49^\circ\)

Example Question #1 : Graphing Functions

Solve for \(\displaystyle n\).

Question_2

(Figure not drawn to scale).

Possible Answers:

\(\displaystyle 8^o\)

\(\displaystyle 12^o\)

\(\displaystyle 14^o\)

\(\displaystyle 10^o\)

Correct answer:

\(\displaystyle 14^o\)

Explanation:

The angles are supplementary, therefore, the sum of the angles must equal \(\displaystyle 180^o\).

\(\displaystyle \small (4n+22^o)+(8n-10^o)=180^o\)

\(\displaystyle \small 4n+22^o+8n-10^o=180^o\)

\(\displaystyle \small 12n+12^o=180^o\)

\(\displaystyle \small 12n=168^o\)

\(\displaystyle \small n=14^o\)

Example Question #2 : Angles

Are \(\displaystyle 129^{\circ}\) and \(\displaystyle 51^{\circ}\) supplementary angles?

Possible Answers:

Yes

No

Not enough information

Correct answer:

Yes

Explanation:

Since supplementary angles must add up to \(\displaystyle 180^{\circ}\), the given angles are indeed supplementary.

Example Question #1 : Understanding Complementary And Suplmentary Angles

Which of the following angles is complementary to \(\displaystyle 32^\circ\)?

Possible Answers:

\(\displaystyle 148^\circ\)

\(\displaystyle 58^\circ\)

\(\displaystyle 158^\circ\)

\(\displaystyle 48^\circ\)

\(\displaystyle 68^\circ\)

Correct answer:

\(\displaystyle 58^\circ\)

Explanation:

Two complementary angles add up to \(\displaystyle 90^\circ\).

\(\displaystyle 90^\circ=32^\circ+x^\circ\)

\(\displaystyle 90^\circ-32^\circ=x^\circ\)

\(\displaystyle 58^\circ=x^\circ\)

Example Question #1 : Angles

What angle is supplementary to \(\displaystyle 142^\circ\)?

Possible Answers:

\(\displaystyle 218^\circ\)

\(\displaystyle 38^\circ\)

\(\displaystyle 48^\circ\)

\(\displaystyle -52^\circ\)

\(\displaystyle 308^\circ\)

Correct answer:

\(\displaystyle 38^\circ\)

Explanation:

When two angles are supplementary, they add up to \(\displaystyle 180^\circ\).

\(\displaystyle 142^\circ+x=180^\circ\)

Solve for \(\displaystyle x\):

\(\displaystyle 142^\circ+x=180^\circ\)

\(\displaystyle x=180^\circ-142^\circ\)

\(\displaystyle x=38^\circ\)

Example Question #3 : Angles

Which of the following angles is coterminal with \(\displaystyle \frac{2\pi}{7}\) ?

Possible Answers:

\(\displaystyle -\frac{2\pi}{7}\)

\(\displaystyle -\frac{12\pi}{7}\)

\(\displaystyle -\frac{9\pi}{7}\)

\(\displaystyle \frac{9\pi}{7}\)

\(\displaystyle \frac{12\pi}{7}\)

Correct answer:

\(\displaystyle -\frac{12\pi}{7}\)

Explanation:

For an angle to be coterminal with \(\displaystyle \theta\), that angle must be of the form \(\displaystyle \theta + 2\pi N\) for some integer \(\displaystyle N\) - or, equivalently, the difference of the angle measures multiplied by \(\displaystyle \frac{1}{2\pi}\)must be an integer. We apply this test to all five choices.

 

\(\displaystyle \frac{9\pi}{7}\):

\(\displaystyle \left ( \frac{1}{2\pi } \right ) \left ( \frac{2\pi}{7} - \frac{9\pi}{7} \right )\)

\(\displaystyle =\left ( \frac{1}{2\pi } \right )\left (- \frac{7\pi}{7} \right ) =\left ( \frac{1}{2\pi } \right ) \pi = \frac{1}{2 }\)

 

\(\displaystyle \frac{12\pi}{7}\):

\(\displaystyle \left ( \frac{1}{2\pi } \right ) \left ( \frac{2\pi}{7} - \frac{12\pi}{7} \right )\)

\(\displaystyle =\left ( \frac{1}{2\pi } \right )\left (- \frac{10\pi}{7} \right ) =- \frac{5}{7}\)

 

\(\displaystyle -\frac{2\pi}{7}\):

\(\displaystyle \left ( \frac{1}{2\pi } \right ) \left [\frac{2\pi}{7} -\left ( -\frac{2\pi}{7} \right ) \right ]\)

\(\displaystyle =\left ( \frac{1}{2\pi } \right )\left ( \frac{2\pi}{7} + \frac{2\pi}{7 }\right )\)

\(\displaystyle =\left ( \frac{1}{2\pi } \right )\left ( \frac{4\pi}{7} \right ) = \frac{2}{7}\)

 

\(\displaystyle -\frac{9\pi}{7}\):

\(\displaystyle \left ( \frac{1}{2\pi } \right ) \left [\frac{2\pi}{7} -\left ( -\frac{9\pi}{7} \right ) \right ]\)

\(\displaystyle =\left ( \frac{1}{2\pi } \right )\left ( \frac{2\pi}{7} + \frac{9\pi}{7 }\right )\)

\(\displaystyle =\left ( \frac{1}{2\pi } \right )\left ( \frac{11\pi}{7} \right ) = \frac{11}{14 }\)

 

\(\displaystyle -\frac{12\pi}{7}\):

\(\displaystyle \left ( \frac{1}{2\pi } \right ) \left [\frac{2\pi}{7} -\left ( -\frac{12\pi}{7} \right ) \right ]\)

\(\displaystyle =\left ( \frac{1}{2\pi } \right )\left ( \frac{2\pi}{7} + \frac{12\pi}{7 }\right )\)

\(\displaystyle =\left ( \frac{1}{2\pi } \right )\left ( \frac{14\pi}{7} \right ) = \left ( \frac{1}{2\pi } \right ) \cdot2\pi = 1\)

 

\(\displaystyle -\frac{12\pi}{7}\) is the correct choice, since only that choice passes our test.

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