Chapter 6: Problem 11
Solve the given trigonometric equation exactly over the indicated interval. $$\tan (2 \theta)=\sqrt{3},-2 \pi \leq \theta<2 \pi$$
Short Answer
Expert verified
The solutions are \(-11\pi/6, -3\pi/2, -5\pi/6, -\pi/3, \pi/6, 2\pi/3, 7\pi/6, 11\pi/6\).
Step by step solution
01
Solve for the angle in radians
The equation is given by \( \tan(2\theta) = \sqrt{3} \). We know that \( \tan(\pi/3) = \sqrt{3} \). So, \( 2\theta = \pi/3 + k\pi \) for some integer \( k \). This is because the tangent function has a period of \( \pi \).
02
Solve for \( \theta \)
To find \( \theta \), divide both sides of the equation \( 2\theta = \pi/3 + k\pi \) by 2. This gives \( \theta = \pi/6 + k\pi/2 \), where \( k \) is an integer.
03
Find solutions within the interval
We need to find all \( \theta \) such that \(-2\pi \leq \theta < 2\pi \). To do this, evaluate \( \theta = \pi/6 + k\pi/2 \) for various integer values of \( k \). Temporarily calculating modest values of \( k \), we use \( k = -4, -3, -2, -1, 0, 1, 2, 3, 4 \). This generates potential solutions.
04
Evaluate integer values of \( k \)
For each \( k \), consider the following calculations:- \( k = -4 \), \( \theta = \pi/6 - 2\pi = -11\pi/6 \)- \( k = -3 \), \( \theta = \pi/6 - 3\pi/2 = -3\pi/2 + \pi/6 = -9\pi/6 = -3\pi/2 \)- \( k = -2 \), \( \theta = \pi/6 - \pi = -5\pi/6 \)- \( k = -1 \), \( \theta = \pi/6 - \pi/2 = -\pi/3 \)- \( k = 0 \), \( \theta = \pi/6 \)- \( k = 1 \), \( \theta = \pi/6 + \pi/2 = 2\pi/3 \)- \( k = 2 \), \( \theta = \pi/6 + \pi = 7\pi/6 \)- \( k = 3 \), \( \theta = \pi/6 + 3\pi/2 = 11\pi/6 \)
05
Ensure values are within the specified range
Check that each \( \theta \) value is within \(-2\pi \leq \theta < 2\pi \). The acceptable solutions are: \(-11\pi/6, -3\pi/2, -5\pi/6, -\pi/3, \pi/6, 2\pi/3, 7\pi/6, 11\pi/6 \). These are the final answers for \( \theta \) within the given range.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Tangent Function
The tangent function, denoted as \( \tan \), is a fundamental concept in trigonometry. It is one of the three primary trigonometric functions, the others being sine and cosine. The tangent of an angle \( \theta \) in a right triangle is the ratio of the length of the opposite side to the adjacent side. Moreover, in the unit circle, it is defined as the ratio of the y-coordinate to the x-coordinate for a point forming angle \( \theta \) with the positive x-axis.
- The tangent function is periodic, with a period of \( \pi \) radians. This means \( \tan(\theta + \pi) = \tan(\theta) \).
- It has an infinite range but is undefined whenever the cosine is zero because it involves division by zero.
- The function produces every real number within its period, and it repeats itself.
Angle in Radians
Radians are a way of measuring angles, distinct from the more common degrees. In simple terms, an angle measured in radians creates an arc on a circle's circumference equal in length to the circle's radius. A complete circle has an angle of \( 2\pi \) radians.
- 1 radian is approximately equal to 57.2958 degrees.
- Commonly used exact values include \( \pi \) radians for a straight angle (180 degrees).
- Radians provide a natural way to express periodic functions, like sine, cosine, and tangent.
Interval Notation
Interval notation is a mathematical notation system that describes a specific range of numbers between two endpoints. It is particularly helpful in describing domains for functions or formulating solution sets of inequalities and equations.
- A closed interval \([a, b]\) includes both endpoints \(a\) and \(b\).
- An open interval \((a, b)\) excludes the endpoints.
- Mixed intervals \((a, b]\) or \([a, b)\) include one endpoint but not the other.