Chapter 8: Problem 6
Solve the triangle, if possible. (triangle can't copy) $$C=22.28^{\circ}, a=25.4 \mathrm{cm}, b=73.8 \mathrm{cm}$$
Short Answer
Expert verified
Triangle is not possible because \( \sin B > 1 \).
Step by step solution
01
Identify Given Information
Given: Angle C = 22.28°, Side a = 25.4 cm, Side b = 73.8 cm. We need to find the other angles A and B, and side c.
02
Use the Law of Sines
The Law of Sines states: \ \[ \frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C} \] \ Using the given values: \ \[ \frac{25.4}{\sin A} = \frac{73.8}{\sin B} = \frac{c}{\sin 22.28^\circ} \]
03
Find Angle A
Rearrange the equation to solve for \(\sin A\): \ \[ \sin A = \sin 22.28^\circ \cdot \frac{25.4}{c} \] \ To find A, we must solve for c first.
04
Solve for Side c
Since \( c = \frac{b \cdot \sin 22.28^\circ}{\sin B} \), we first need to find another angle. Use \( \sin B = \frac{b \cdot \sin A}{a} \), and solve for \( B \).
05
Determine Angle B
Use the identity: \ \[ \sin B = \frac{73.8 \cdot \sin 22.28^\circ}{25.4} \] \ Calculate the value of \( \sin B = \frac{73.8 \cdot 0.3782}{25.4} \approx 1.099 \). This value is greater than 1, thus it’s not possible for a valid triangle.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Law of Sines
The Law of Sines is a fundamental principle in trigonometry that relates the sides and angles of a triangle. It's particularly useful for solving triangles when given either two angles and one side (AAS or ASA), or two sides and a non-included angle (SSA).
The formula for the Law of Sines is: \ \( \frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C} \).
This equation tells us that the ratio of the length of a side of a triangle to the sine of the opposite angle is the same for all three sides and angles.
To use the Law of Sines:
The formula for the Law of Sines is: \ \( \frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C} \).
This equation tells us that the ratio of the length of a side of a triangle to the sine of the opposite angle is the same for all three sides and angles.
To use the Law of Sines:
- Identify and label the known angles and sides.
- Set up the ratios based on the known values.
- Solve for the unknown angles and sides using algebraic manipulation and trigonometric functions.
Triangle Properties
Understanding triangle properties is crucial in trigonometry. Here are some key properties:
There are different types of triangles based on sides and angles:
- **Triangles are 2D shapes with three sides and three angles.**
- **The sum of the interior angles of any triangle is always 180 degrees.**
- **The longest side is opposite the largest angle, and the shortest side is opposite the smallest angle.**
There are different types of triangles based on sides and angles:
- **Scalene Triangle:** All sides and angles are different.
- **Isosceles Triangle:** Two sides are equal, and the angles opposite those sides are equal.
- **Equilateral Triangle:** All three sides and angles are equal.
- **Acute Triangle:** All angles are less than 90 degrees.
- **Right Triangle:** One angle is exactly 90 degrees.
- **Obtuse Triangle:** One angle is greater than 90 degrees.
Also, the angles can classify triangles as:
Angle Calculation
Calculating angles in a triangle involves using various trigonometric principles. Here are the steps for calculating angles:
In the given problem, we found:
\ \( \text{Angle B:} \ \sin B = \frac{73.8 \cdot \sin 22.28^{\circ}}{25.4} \). However, the result \approx 1.099 is not valid for a sine function (which ranges from -1 to 1). This means the triangle as described cannot exist. Therefore, when solving triangles, validate each step to avoid such inconsistencies.
- **Identify the given information:** List all known sides and angles.
- **Use relevant trigonometric formulas:** Based on known values, choose the appropriate formula.
- **Apply the Law of Sines or Law of Cosines:** These laws relate the angles to the sides of the triangle.
- **Check the sum of angles:** Ensure the sum is 180 degrees to verify the calculations.
\ \( \text{For example, if you need to find angle A when two sides a and b are known: } \ \sin A = \sin C \cdot \frac{a}{c} \).
In the given problem, we found:
\ \( \text{Angle B:} \ \sin B = \frac{73.8 \cdot \sin 22.28^{\circ}}{25.4} \). However, the result \approx 1.099 is not valid for a sine function (which ranges from -1 to 1). This means the triangle as described cannot exist. Therefore, when solving triangles, validate each step to avoid such inconsistencies.