Example: Trig to solve the sides and angles of a right triangle | Trigonometry

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This lesson provides a step-by-step guide on solving a right triangle by determining the lengths of its sides and the measures of its angles using trigonometric functions. By applying the tangent function to find side \( a \) and the cosine function for side \( b \), we calculated their lengths to be approximately 10.7 and 11.8, respectively, while also determining the measure of the remaining angle \( W \) to be 25 degrees. The lesson emphasizes the use of trigonometric relationships and triangle properties to find unknown values in right triangles.

Solving a Right Triangle: A Step-by-Step Guide

In this article, we’ll explore how to solve a right triangle by finding the lengths of all sides and the measures of all angles. We’ll use trigonometric functions and triangle properties to help us out.

Understanding the Problem

When solving a right triangle, our goal is to find the lengths of all sides (which we’ll call ( a ) and ( b )) and the measures of all angles. In this example, we know two angles and need to find the third angle and the lengths of the sides.

Finding Side ( a )

To find the length of side ( a ), we use the tangent function. This function connects the opposite side to the adjacent side in a right triangle. We know angle ( Y ) is 65 degrees, and the adjacent side is 5. So, we set up this equation:

(tan(65^circ) = frac{a}{5})

To solve for ( a ), we rearrange the equation:

(a = 5 cdot tan(65^circ))

Using a calculator, we find:

(a approx 5 cdot 2.1445 approx 10.7)

So, the length of side ( a ) is approximately 10.7.

Finding Side ( b )

Next, we find the length of side ( b ), the hypotenuse. We use the cosine function because we know the adjacent side (5) and need to find the hypotenuse:

(cos(65^circ) = frac{5}{b})

Rearranging gives us:

(b cdot cos(65^circ) = 5)

To solve for ( b ), divide both sides by (cos(65^circ)):

(b = frac{5}{cos(65^circ)})

Using a calculator, we find:

(b approx frac{5}{0.4226} approx 11.8)

Therefore, the length of side ( b ) is approximately 11.8.

Finding Angle ( W )

Finally, we find the measure of angle ( W ). The sum of the angles in a triangle is always 180 degrees. In our right triangle:

(W + 65^circ + 90^circ = 180^circ)

Simplifying, we get:

(W + 155^circ = 180^circ)

Subtracting 155 degrees from both sides gives us:

(W = 25^circ)

Conclusion

In summary, we’ve successfully solved the right triangle. The lengths of the sides are approximately:

  • Side ( a ): 10.7
  • Side ( b ): 11.8

And the measure of angle ( W ) is 25 degrees. This process shows how trigonometric functions and triangle properties help us find unknown values.

  1. What new insights did you gain about solving right triangles from the article?
  2. How did the use of trigonometric functions enhance your understanding of right triangle properties?
  3. Can you think of any real-world applications where solving a right triangle might be useful?
  4. What challenges might you face when applying these methods to solve a right triangle, and how could you overcome them?
  5. How does understanding the relationship between angles and sides in a right triangle help in other areas of mathematics?
  6. Reflect on a time when you had to solve a problem involving triangles. How would the techniques from the article have helped you?
  7. What questions do you still have about the process of solving right triangles after reading the article?
  8. How might you explain the process of solving a right triangle to someone who is new to trigonometry?
  1. Interactive Triangle Solver

    Use an online interactive triangle calculator to input different angles and side lengths. Experiment with changing these values and observe how the other sides and angles adjust. This will help you understand the relationships between the sides and angles in a right triangle.

  2. Trigonometric Function Matching Game

    Create flashcards with different trigonometric functions and their corresponding formulas. Match each function to its correct formula and use them to solve for unknown sides or angles in various right triangle problems.

  3. Angle and Side Length Estimation Challenge

    Work in pairs to estimate the missing angles and side lengths of a right triangle given only one angle and one side. Compare your estimates with the actual values calculated using trigonometric functions to see how close you were.

  4. Real-World Triangle Application

    Identify real-world objects or structures that form right triangles, such as ladders against walls or ramps. Measure the angles and one side, then calculate the other sides using trigonometric functions to see how these concepts apply in real life.

  5. Right Triangle Puzzle

    Create a puzzle where each piece represents a part of a right triangle problem, such as an angle, side, or trigonometric function. Assemble the pieces to solve the triangle, reinforcing your understanding of how each component fits together.

TriangleA polygon with three edges and three vertices. – In trigonometry, we often study the properties of a right triangle to understand the relationships between its angles and sides.

AngleThe figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle. – The sum of the angles in any triangle is always 180 degrees.

SideOne of the line segments that make up a polygon. – In a right triangle, the longest side is called the hypotenuse.

TangentA trigonometric function that represents the ratio of the opposite side to the adjacent side of a right triangle. – To find the tangent of an angle, divide the length of the opposite side by the length of the adjacent side.

CosineA trigonometric function that represents the ratio of the adjacent side to the hypotenuse of a right triangle. – The cosine of a 60-degree angle is 0.5.

DegreesA unit of measurement for angles, where a full circle is 360 degrees. – In trigonometry, angles are often measured in degrees or radians.

HypotenuseThe longest side of a right triangle, opposite the right angle. – According to the Pythagorean theorem, the square of the hypotenuse is equal to the sum of the squares of the other two sides.

OppositeThe side of a right triangle that is opposite a given angle. – In a right triangle, the sine of an angle is the ratio of the length of the opposite side to the hypotenuse.

AdjacentThe side of a right triangle that forms one of the sides of a given angle, excluding the hypotenuse. – The cosine of an angle in a right triangle is the ratio of the length of the adjacent side to the hypotenuse.

PropertiesCharacteristics or attributes that help define the nature of geometric figures. – Understanding the properties of triangles is essential for solving trigonometric problems.

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