Chapter 5: Problem 10
Given the indicated parts of triangle \(A B C\) with \(\gamma=90^{\circ},\) approximate the remaining parts. $$\beta=64^{\circ} 20^{\prime}, \quad a=20.1$$
Short Answer
Expert verified
\(\alpha = 25^{\circ} 40^{\prime}\); \(b \approx 9.14\); \(c \approx 22.38\).
Step by step solution
01
Identify Known Values
In triangle \(ABC\), we know that \(\gamma = 90^{\circ}\) (since it is a right triangle), \(\beta = 64^{\circ} 20^{\prime}\), and the side \(a = 20.1\). We need to find the other angle \(\alpha\), and the remaining sides \(b\) and \(c\).
02
Calculate Angle \(\alpha\)
Since the sum of angles in any triangle is \(180^{\circ}\), we can find \(\alpha\) by using the equation: \[\alpha = 180^{\circ} - \beta - \gamma.\]Substitute the known values:\[\alpha = 180^{\circ} - 64^{\circ} 20^{\prime} - 90^{\circ} = 25^{\circ} 40^{\prime}.\]
03
Calculate Side \(b\) Using Trigonometry
Using the tangent function, which is the ratio of the opposite side to the adjacent side in a right triangle, we have:\[\tan(\beta) = \frac{a}{b}.\]Solving for \(b\):\[b = \frac{a}{\tan(\beta)}.\]Substitute \(a = 20.1\) and \(\beta = 64^{\circ} 20^{\prime}\):\[b \approx \frac{20.1}{\tan(64^{\circ} 20^{\prime})} \approx 9.14.\]
04
Calculate Hypotenuse \(c\) Using Trigonometry
We use the sine function, which is the ratio of the opposite side to the hypotenuse:\[\sin(\beta) = \frac{a}{c}.\]Solving for \(c\):\[c = \frac{a}{\sin(\beta)}.\]Substitute \(a = 20.1\) and \(\beta = 64^{\circ} 20^{\prime}\):\[c \approx \frac{20.1}{\sin(64^{\circ} 20^{\prime})} \approx 22.38.\]
05
Verification Step: Check Calculations
Double-check calculations by computing the cosine of \(\beta\) and verifying side \(b\) using:\[\cos(\beta) = \frac{b}{c}.\]Calculate \(\cos(64^{\circ} 20^{\prime})\) and compare \(b\):\[\cos(64^{\circ} 20^{\prime}) \approx 0.435\quad \Rightarrow \quad b \approx c \times 0.435 \approx 9.14.\]The values are consistent, ensuring calculations are correct.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Trigonometric Functions
Trigonometric functions are fundamental tools in understanding right triangles. When dealing with a right triangle, the main functions used are sine (\(\sin\)), cosine (\(\cos\)), and tangent (\(\tan\)). These functions help relate the angles to the sides of the triangle.
- Sine of an angle is the ratio of the length of the side opposite the angle to the hypotenuse.
- Cosine of an angle is the ratio of the length of the adjacent side to the hypotenuse.
- Tangent of an angle is the ratio of the length of the side opposite the angle to the adjacent side.
Angle Sum Property
The angle sum property is a fundamental concept in trigonometry and geometry. It states that the sum of the angles in any triangle is always \(180^{\circ}\). This is particularly helpful in right triangles where one angle is always \(90^{\circ}\).
To find an unknown angle in a triangle, simply subtract the known angles from \(180^{\circ}\). For example, if you have a right triangle with the angles \(\gamma = 90^{\circ}\) and \(\beta = 64^{\circ} 20^{\prime}\), you can find the third angle \(\alpha\) by calculating:\[\alpha = 180^{\circ} - 90^{\circ} - 64^{\circ} 20^{\prime}\]which equals \(25^{\circ} 40^{\prime}\). This property ensures you can always determine one unknown angle if the other two are known.
To find an unknown angle in a triangle, simply subtract the known angles from \(180^{\circ}\). For example, if you have a right triangle with the angles \(\gamma = 90^{\circ}\) and \(\beta = 64^{\circ} 20^{\prime}\), you can find the third angle \(\alpha\) by calculating:\[\alpha = 180^{\circ} - 90^{\circ} - 64^{\circ} 20^{\prime}\]which equals \(25^{\circ} 40^{\prime}\). This property ensures you can always determine one unknown angle if the other two are known.
Triangle Side Lengths
Understanding side lengths in a right triangle involves using trigonometric relationships. With a right triangle, we have the hypotenuse, opposite side, and adjacent side. Depending on the known values, you can calculate the missing sides using trigonometric functions like sine, cosine, and tangent.
- Use the tangent function when you know an angle and one side, solving for the opposite or adjacent side.
- Employ the sine function to find the hypotenuse or opposite when you have an angle and another side.