Chapter 9: Problem 7
Solve the triangles with the given parts. $$a=4.601, b=3.107, A=18.23^{\circ}$$
Short Answer
Expert verified
The triangle has angles \(A = 18.23^{\circ}\), \(B = 12.19^{\circ}\), \(C = 149.58^{\circ}\) and sides \(a = 4.601\), \(b = 3.107\), \(c = 8.569\).
Step by step solution
01
Identify Triangle Data
We're given two sides and an angle: side \(a = 4.601\), side \(b = 3.107\), and angle \(A = 18.23^{\circ}\). Since two sides and a non-included angle are known, we'll use the Law of Sines to find the remaining parts.
02
Apply the Law of Sines
According to the Law of Sines, \(\frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C}\). We'll first find angle \(B\) by using the equation \(\frac{a}{\sin A} = \frac{b}{\sin B}\). Substitute the known values: \[ \frac{4.601}{\sin 18.23^{\circ}} = \frac{3.107}{\sin B} \]Calculate \(\sin 18.23^{\circ}\) to solve for \(\sin B\).
03
Solve for \(\sin B\)
Calculate \(\sin 18.23^{\circ}\) using a calculator:\(\sin 18.23^{\circ} \approx 0.312\).Multiply both sides by \(\sin B\) and divide by \(4.601\):\[ \sin B = \frac{3.107 \times 0.312}{4.601} \approx 0.210 \]Now, find angle \(B\) by taking the inverse sine:\( B = \sin^{-1}(0.210) \approx 12.19^{\circ}\).
04
Calculate Angle C
With angles \(A\) and \(B\) known, calculate angle \(C\). Since the angles of a triangle sum up to \(180^{\circ}\), we have:\[ C = 180^{\circ} - 18.23^{\circ} - 12.19^{\circ} \approx 149.58^{\circ} \]
05
Use Law of Sines Again to Find Side c
Now that we have angle \(C\), use the Law of Sines again to find side \(c\):\[ \frac{c}{\sin C} = \frac{a}{\sin A} \]Substitute the known values and calculate \(\sin 149.58^{\circ}\):\[ c = \frac{4.601 \times \sin 149.58^{\circ}}{0.312} \approx 8.569 \]
06
Verify the Solution
Confirm the calculations: angles \(A\), \(B\), and \(C\) should sum to \(180^{\circ}\) and all sides and angles should satisfy the Law of Sines.The calculated values satisfy these conditions, verifying the solution.
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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 powerful tool in trigonometry used to solve triangles, especially when you have two angles and one side (AAS or ASA) or two sides and a non-included angle (SSA). This law states:
In practice, calculate one unknown angle first and ensure that triangle properties and trigonometric rules are honored. Double-check solutions as shown in the exercise to ensure accuracy.
- For a triangle with sides \(a\), \(b\), and \(c\) opposite angles \(A\), \(B\), and \(C\) respectively: \( \frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C} \).
In practice, calculate one unknown angle first and ensure that triangle properties and trigonometric rules are honored. Double-check solutions as shown in the exercise to ensure accuracy.
triangle solving
Solving a triangle means finding all its unknown sides and angles. In a problem like this, where you are given two sides and a non-included angle, it often involves several strategies:
This structured approach simplifies complex problems and ensures all triangle properties are respected.
- First, identify what you know, and decide which rule to apply. The Law of Sines is particularly useful in this SSA (Side-Side-Angle) scenario.
- Use the known information to find unknown angles or sides step-by-step. It's often helpful to work systematically through the options.
This structured approach simplifies complex problems and ensures all triangle properties are respected.
inverse sine
Inverse sine, denoted \(\sin^{-1}\) or arcsin, is used to find an angle when you know its sine. This concept is crucial in triangle solving exercises such as this one.
When trying to find an angle given a sine value:
This process makes it a key tool in verifying and solving for unknown angles in triangle problems where the use of trigonometric ratios is required.
When trying to find an angle given a sine value:
- Use \(\sin^{-1}(x)\) to find an angle whose sine is \(x\).
- This function will give you an angle in the range from \(-90^{\circ}\) to \(90^{\circ}\) for real numbers within \(-1\) to \(1\).
This process makes it a key tool in verifying and solving for unknown angles in triangle problems where the use of trigonometric ratios is required.