Chapter 6: Problem 16
13-18 $$ Sketch each triangle, and then solve the triangle using the Law of Sines. $$ \angle A=22^{\circ}, \quad \angle B=95^{\circ}, \quad a=420 $$
Short Answer
Expert verified
Angles: \(22^\circ, 95^\circ, 63^\circ\), Sides: \(a = 420, b \approx 1116.96, c \approx 998.54\). Sketch with labeled dimensions.
Step by step solution
01
Identify Given Information
We have a triangle with \( \angle A = 22^\circ \), \( \angle B = 95^\circ \), and side \( a = 420 \).
02
Determine the Missing Angle
Since the sum of the angles in a triangle is \( 180^\circ \), find \( \angle C \): \[ \angle C = 180^\circ - \angle A - \angle B = 180^\circ - 22^\circ - 95^\circ = 63^\circ. \]
03
Apply the Law of Sines
Use the law of sines to find side \( b \): \[ \frac{a}{\sin A} = \frac{b}{\sin B}. \] Substitute the known values: \[ \frac{420}{\sin 22^\circ} = \frac{b}{\sin 95^\circ}. \]
04
Solve for Side b
Rearrange the equation to solve for \( b \): \[ b = \frac{420 \cdot \sin 95^\circ}{\sin 22^\circ}. \] Calculate using the sine values: \( \sin 22^\circ \approx 0.3746 \) and \( \sin 95^\circ \approx 0.9962 \). Then: \[ b \approx \frac{420 \cdot 0.9962}{0.3746} \approx 1116.96. \]
05
Solve for Side c
Use the law of sines again to find side \( c \): \[ \frac{a}{\sin A} = \frac{c}{\sin C}. \] Substitute the known values: \[ \frac{420}{\sin 22^\circ} = \frac{c}{\sin 63^\circ}. \] Rearrange to solve for \( c \): \[ c = \frac{420 \cdot \sin 63^\circ}{\sin 22^\circ}. \] Calculate using \( \sin 63^\circ \approx 0.8910 \): \[ c \approx \frac{420 \cdot 0.8910}{0.3746} \approx 998.54. \]
06
Sketch the Triangle
Create a diagram with angles \( 22^\circ \), \( 95^\circ \), and \( 63^\circ \), and label sides \( a = 420 \), \( b \approx 1116.96 \), and \( c \approx 998.54 \). The sketch should reflect these dimensions accurately.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Triangle Solving
Solving a triangle involves finding all its angles and sides. When you're given certain angles and one side, like side \( a = 420 \) and angles \( A = 22^{\circ} \) and \( B = 95^{\circ} \), it's about figuring out the rest using known formulas. Here's a step-by-step guide on how to do it:
- Identify given information: Start by noting down the given angles and side.
- Find the missing angle: Use the Angle Sum Property (more on this later) to find the third angle.
- Apply the Law of Sines: This will help you find the other two sides.
- Verify and sketch: Finally, sketch the triangle to ensure it makes sense visually.
Angle Sum Property
The Angle Sum Property is a fundamental rule in geometry applied to triangles. It states that the sum of the interior angles in a triangle is always equal to \( 180^{\circ} \).For instance, if you know two angles of a triangle, you can easily determine the third:- Given \( \angle A = 22^{\circ} \) and \( \angle B = 95^{\circ} \), you can find the third angle using: \[ \angle C = 180^{\circ} - \angle A - \angle B = 180^{\circ} - 22^{\circ} - 95^{\circ} = 63^{\circ}. \]This property is essential for solving triangles because it provides a straightforward method to find an unknown angle, which is crucial for subsequent calculations.
Sketching Triangles
Sketching triangles from given data helps visualize the problem and verify your calculations. Start with a rough sketch based on the angles and side you know. Here’s how:- Draw the known side: In our problem, since \( a = 420 \) is given, draw this line first.- Mark given angles: Angle \( A = 22^{\circ} \) and \( \angle B = 95^{\circ} \) are placed correctly following the known sides.- Complete the triangle: Use the Angle Sum Property to place the final angle \( \angle C = 63^{\circ} \).Ensure the sketch represents the angles correctly—this visual confirmation can often highlight any discrepancies in your results before you go further.
Trigonometry
Trigonometry is a branch of mathematics that studies the relationships between the angles and sides of triangles. In this problem, the Law of Sines is particularly useful:This law is expressed as:\[ \frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C}, \]where \( a \), \( b \), and \( c \) are sides opposite angles \( A \), \( B \), and \( C \) respectively. It's used to find unknown sides or angles when some of the triangle's characteristics are known. For example, to find side \( b \) we rearrange the formula:\[ b = \frac{420 \cdot \sin 95^{\circ}}{\sin 22^{\circ}} \approx 1116.96. \]This formula can be used similarly to find \( c \) and is crucial in solving any non-right triangle accurately.