High School Math : Applying Trigonometric Functions

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Triangles

Rt_triangle_lettersIn this figure, side \(\displaystyle X=20\)\(\displaystyle Y=13\), and \(\displaystyle c=90^\circ\). What is the value of angle \(\displaystyle a\)?

Possible Answers:

\(\displaystyle 40.54^\circ\)

Undefined

\(\displaystyle 6.5^\circ\)

\(\displaystyle 90^\circ\)

\(\displaystyle 49.46^\circ\)

Correct answer:

\(\displaystyle 49.46^\circ\)

Explanation:

Since \(\displaystyle c=90^\circ\), we know we are working with a right triangle.

That means that \(\displaystyle \cos(\theta)=\frac{\text{adjacent}}{\text{hypotenuse}}\).

In this problem, that would be:

\(\displaystyle \cos(a)=\frac{\text{Y}}{\text{X}}\)

Plug in our given values:

\(\displaystyle \cos(a)=\frac{\text{13}}{\text{20}}\)

\(\displaystyle \cos(a)=0.65\)

\(\displaystyle a=\cos^{-1}(0.65)\)

\(\displaystyle a=49.46^\circ\)

Example Question #1 : Right Triangles

Let ABC be a right triangle with sides \(\displaystyle A\) = 3 inches, \(\displaystyle B\) = 4 inches, and \(\displaystyle C\) = 5 inches. In degrees, what is the \(\displaystyle \sin \Theta\) where \(\displaystyle \Theta\) is the angle opposite of side \(\displaystyle A\)?

Possible Answers:

\(\displaystyle .3\)

\(\displaystyle .5\)

\(\displaystyle .6\)

\(\displaystyle .7\)

\(\displaystyle .4\)

Correct answer:

\(\displaystyle .6\)

Explanation:

3-4-5_triangle

We are looking for \(\displaystyle \sin(\theta )\). Remember the definition of \(\displaystyle sin\) in a right triangle is the length of the opposite side divided by the length of the hypotenuse. 

So therefore, without figuring out \(\displaystyle \Theta\) we can find

\(\displaystyle \sin \Theta =\frac{3}{5}=.6\)

Example Question #1 : Trigonometric Functions

Rt_triangle_letters

In this figure, if angle \(\displaystyle c=90^\circ\), side \(\displaystyle X=12\), and side \(\displaystyle Z=8\), what is the measure of angle \(\displaystyle a\)?

Possible Answers:

\(\displaystyle 41.8^\circ\)

\(\displaystyle 90^\circ\)

\(\displaystyle \frac{2}{3}^\circ\)

\(\displaystyle 48.2^\circ\)

Undefined

Correct answer:

\(\displaystyle 41.8^\circ\)

Explanation:

Since \(\displaystyle c=90^\circ\), we know we are working with a right triangle.

That means that \(\displaystyle \sin(\theta)=\frac{\text{opposite}}{\text{hypotenuse}}\).

In this problem, that would be:

\(\displaystyle \sin(a)=\frac{\text{Z}}{\text{X}}\)

Plug in our given values:

\(\displaystyle \sin(a)=\frac{8}{12}\)

\(\displaystyle \sin(a)=\frac{2}{3}\)

\(\displaystyle a=\sin^{-1}(\frac{2}{3})\)

\(\displaystyle a=41.8^\circ\)

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