Chapter 1: Problem 72
Solve \(\sec ^{2} x=\sqrt{3} \tan x+1\) on \([0, \pi)\).
Short Answer
Expert verified
The solutions are \(x = 0\) and \(x = \frac{\pi}{3}\).
Step by step solution
01
Substitute Trigonometric Identities
We start by using the identity for secant squared and tangent: \(\sec^2 x = 1 + \tan^2 x\). This gives us the equation \(1 + \tan^2 x = \sqrt{3} \tan x + 1\).
02
Simplify the Equation
Subtract 1 from both sides to remove the constant term, leading to the equation \(\tan^2 x = \sqrt{3} \tan x\).
03
Factor the Equation
We can factor the equation as \(\tan x (\tan x - \sqrt{3}) = 0\). This implies two scenarios: either \(\tan x = 0\) or \(\tan x = \sqrt{3}\).
04
Solve for \(\tan x = 0\)
We find \(\tan x = 0\) at \(x = 0\) and \(x = \pi\). Since the interval is \([0, \pi)\), only \(x = 0\) is included.
05
Solve for \(\tan x = \sqrt{3}\)
This occurs when \(x = \frac{\pi}{3}\) and its periodic equivalent. Within the interval \([0, \pi)\), this corresponds to \(x = \frac{\pi}{3}\).
06
Combine Solutions
The solutions for \(x\) within the interval \([0, \pi)\) are \(x = 0\) and \(x = \frac{\pi}{3}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Secant Function
The secant function, denoted as \( \sec x \), is the reciprocal of the cosine function. Mathematically, it is expressed as \( \sec x = \frac{1}{\cos x} \). Understanding the secant function is critical to solving trigonometric equations, as it often appears in problems involving angles and their relationships. When dealing with secant, it is important to remember:
- The secant function is undefined wherever the cosine is zero because division by zero is undefined.
- Characteristics: It has the same period and vertical asymptotes as the tangent function, occurring where \( \cos x = 0 \).
- Graphically, the secant function exhibits vertical "spikes" at each of these asymptotes and fluctuates above and below the x-axis.
Tangent Function
The tangent function, represented as \( \tan x \), relates to sine and cosine through the formula \( \tan x = \frac{\sin x}{\cos x} \). It is crucial to comprehend this function in trigonometric equations because:
- The tangent function describes the slope of the angle formed with the x-axis.
- It has periodic properties, repeating every \( \pi \) radians. This means any solution within a cycle can be repeated for other cycles.
- There are vertical asymptotes wherever the cosine function is zero, similar to the secant function.
Factoring Equations
Factoring is a powerful algebraic tool used to solve equations efficiently. In the context of trigonometric equations, it involves expressing a polynomial equation in terms of its factors. This method simplifies the equation, allowing us to identify solutions quickly. Here is why factoring is useful:
- It breaks down complex expressions into simpler components, helping identify possible solutions.
- By setting each factor equal to zero, it offers a clear path to finding the roots of the equation.
- In trigonometric problems, factoring can reveal specific angles or values that solve the equation, as seen in our step-by-step solution using \( \tan x (\tan x - \sqrt{3}) = 0 \).
Trigonometric Identities
Trigonometric identities are formulas that express relationships between the angles and sides of a triangle. They are immensely useful in simplifying trigonometric equations, allowing for straightforward solutions. Key identities include:
- Pythagorean identities: Used in this exercise is \( \sec^2 x = 1 + \tan^2 x \), which connects secant and tangent.
- Reciprocal identities: These include \( \tan x = \frac{\sin x}{\cos x} \), essential for simplifying expressions.
- Angle-sum identities: Though not directly used here, these assist in combining angles efficiently in more complex problems.