Using Sine to Find the Measure of an Acute Angle

Oct 13, 2025 by wbrum.org 58 views

Introduction

In trigonometry, the sine, cosine, and tangent functions are used to relate the angles of a right triangle to the ratios of the lengths of its sides. Given the value of one of these trigonometric functions, we can find the measure of an acute angle. In this article, we will explore how to find the measure of an acute angle using the given values of sine, cosine, and tangent.

Using Sine to Find the Measure of an Acute Angle

The sine function is defined as the ratio of the length of the opposite side to the length of the hypotenuse in a right triangle. If we are given the value of the sine function, we can use the inverse sine function to find the measure of the acute angle.

Example 1: Finding the Measure of an Acute Angle Using Sine

Given that $\sin A = 0.173648$ , we can use the inverse sine function to find the measure of the acute angle $A$ . The inverse sine function is denoted by $\sin^{-1}$ .

$\sin A = 0.173648$

$\sin^{-1}(\sin A) = \sin^{-1}(0.173648)$

Using a calculator, we can find that $\sin^{-1}(0.173648) \approx 9.97^{\circ}$ .

Therefore, the measure of the acute angle $A$ is approximately $9.97^{\circ}$ .

Using Cosine to Find the Measure of an Acute Angle

The cosine function is defined as the ratio of the length of the adjacent side to the length of the hypotenuse in a right triangle. If we are given the value of the cosine function, we can use the inverse cosine function to find the measure of the acute angle.

Example 2: Finding the Measure of an Acute Angle Using Cosine

Given that $\cos A = 0.961262$ , we can use the inverse cosine function to find the measure of the acute angle $A$ . The inverse cosine function is denoted by $\cos^{-1}$ .

$\cos A = 0.961262$

$\cos^{-1}(\cos A) = \cos^{-1}(0.961262)$

Using a calculator, we can find that $\cos^{-1}(0.961262) \approx 15.02^{\circ}$ .

Therefore, the measure of the acute angle $A$ is approximately $15.02^{\circ}$ .

Using Tangent to Find the Measure of an Acute Angle

The tangent function is defined as the ratio of the length of the opposite side to the length of the adjacent side in a right triangle. If we are given the value of the tangent function, we can use the inverse tangent function to find the measure of the acute angle.

Example 3: Finding the Measure of an Acute Angle Using Tangent

Given that $\tan A = 0.60086$ , we can use the inverse tangent function to find the measure of the acute angle $A$ . The inverse tangent function is denoted by $\tan^{-1}$ .

$\tan A = 0.60086$

$\tan^{-1}(\tan A) = \tan^{-1}(0.60086)$

Using a calculator, we can find that $\tan^{-1}(0.60086) \approx 30.86^{\circ}$ .

Therefore, the measure of the acute angle $A$ is approximately $30.86^{\circ}$ .

Using Sine to Find the Measure of an Acute Angle (Example 4)

Given that $\sin A = 0.798636$ , we can use the inverse sine function to find the measure of the acute angle $A$ .

$\sin A = 0.798636$

$\sin^{-1}(\sin A) = \sin^{-1}(0.798636)$

Using a calculator, we can find that $\sin^{-1}(0.798636) \approx 53.13^{\circ}$ .

Therefore, the measure of the acute angle $A$ is approximately $53.13^{\circ}$ .

Conclusion

In this article, we have explored how to find the measure of an acute angle using the given values of sine, cosine, and tangent. We have used the inverse sine, cosine, and tangent functions to find the measure of the acute angle. The examples provided demonstrate how to use these functions to find the measure of an acute angle.

References

"Trigonometry" by Michael Corral
"Precalculus" by James Stewart
"Trigonometry for Dummies" by Mary Jane Sterling

Q: What is an acute angle?

A: An acute angle is an angle whose measure is between 0° and 90°.

Q: What is the sine function?

A: The sine function is a trigonometric function that relates the ratio of the length of the opposite side to the length of the hypotenuse in a right triangle.

Q: How do I use the sine function to find the measure of an acute angle?

A: To use the sine function to find the measure of an acute angle, you need to know the value of the sine function and use the inverse sine function to find the measure of the angle.

Q: What is the cosine function?

A: The cosine function is a trigonometric function that relates the ratio of the length of the adjacent side to the length of the hypotenuse in a right triangle.

Q: How do I use the cosine function to find the measure of an acute angle?

A: To use the cosine function to find the measure of an acute angle, you need to know the value of the cosine function and use the inverse cosine function to find the measure of the angle.

Q: What is the tangent function?

A: The tangent function is a trigonometric function that relates the ratio of the length of the opposite side to the length of the adjacent side in a right triangle.

Q: How do I use the tangent function to find the measure of an acute angle?

A: To use the tangent function to find the measure of an acute angle, you need to know the value of the tangent function and use the inverse tangent function to find the measure of the angle.

Q: What is the inverse sine function?

A: The inverse sine function is a function that takes the value of the sine function and returns the measure of the angle.

Q: What is the inverse cosine function?

A: The inverse cosine function is a function that takes the value of the cosine function and returns the measure of the angle.

Q: What is the inverse tangent function?

A: The inverse tangent function is a function that takes the value of the tangent function and returns the measure of the angle.

Q: How do I use a calculator to find the measure of an acute angle?

A: To use a calculator to find the measure of an acute angle, you need to enter the value of the trigonometric function and use the inverse function to find the measure of the angle.

Q: What are some common mistakes to avoid when finding the measure of an acute angle?

A: Some common mistakes to avoid when finding the measure of an acute angle include:

Not using the correct trigonometric function
Not using the inverse function
Not checking the units of the angle
Not rounding the answer to the correct number of decimal places

Q: How do I check my answer when finding the measure of an acute angle?

A: To check your answer when finding the measure of an acute angle, you can use a calculator to find the value of the trigonometric function and compare it to the value you entered. You can also use a trigonometric table or a graphing calculator to check your answer.

Q: What are some real-world applications of finding the measure of an acute angle?

A: Some real-world applications of finding the measure of an acute angle include:

Building design: Architects use trigonometry to design buildings and ensure that the angles of the walls and roof are correct.
Engineering: Engineers use trigonometry to design bridges and ensure that the angles of the supports are correct.
Navigation: Pilots use trigonometry to navigate and ensure that the angles of the aircraft are correct.
Surveying: Surveyors use trigonometry to measure the angles of the land and ensure that the boundaries are correct.

Conclusion

In this article, we have answered some frequently asked questions about finding the measure of an acute angle. We have covered the basics of trigonometry, including the sine, cosine, and tangent functions, and how to use them to find the measure of an acute angle. We have also covered some common mistakes to avoid and how to check your answer. Finally, we have discussed some real-world applications of finding the measure of an acute angle.