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Ch. 7 - Applications of Trigonometry and Vectors
Chapter 8, Problem 6.31

Apply the law of sines to the following: a = √5, c = 2√5, A = 30°. What is the value of ​sin​ ​C​​? What is the measure​ of ​​​​C​​​? Based on it​​s angle measures, what kind of triangle is triangl​e ​​ABC​​​?

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Step 1: Recall the Law of Sines, which states that \( \frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C} \).
Step 2: Substitute the known values into the Law of Sines: \( \frac{\sqrt{5}}{\sin 30^\circ} = \frac{2\sqrt{5}}{\sin C} \).
Step 3: Calculate \( \sin 30^\circ \), which is \( \frac{1}{2} \), and substitute it into the equation.
Step 4: Solve for \( \sin C \) by cross-multiplying and simplifying the equation.
Step 5: Use the inverse sine function to find the measure of angle \( C \), and determine the type of triangle based on its angle measures.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Law of Sines

The Law of Sines states that in any triangle, the ratio of the length of a side to the sine of its opposite angle is constant. This can be expressed as a/sin(A) = b/sin(B) = c/sin(C). It is particularly useful for solving triangles when given two angles and one side or two sides and a non-included angle.
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Intro to Law of Sines

Sine Function

The sine function is a fundamental trigonometric function defined for an angle in a right triangle as the ratio of the length of the opposite side to the hypotenuse. It is crucial for calculating the angles and sides of triangles using the Law of Sines, as it helps determine the values of angles based on the lengths of the sides.
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Types of Triangles

Triangles can be classified based on their angles: acute (all angles less than 90°), right (one angle exactly 90°), and obtuse (one angle greater than 90°). Understanding the type of triangle is essential for determining its properties and solving related problems, especially when using the Law of Sines to find unknown angles.
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