Chapter 7: Problem 2
Find all solutions of the equation. $$\sin x+1=0$$
Short Answer
Expert verified
The solutions are \( x = \frac{3\pi}{2} + 2k\pi \), where \( k \) is any integer.
Step by step solution
01
Understand the Equation
The given equation is \( \sin x + 1 = 0 \). Our goal is to find values of \( x \) that satisfy this equation. First, we'll isolate the sine function by subtracting 1 from both sides to get \( \sin x = -1 \).
02
Identify the Sine Function Value
Recall that the sine function \( \sin x \) reaches -1 at specific points on the unit circle. Specifically, \( \sin x = -1 \) at \( x = \frac{3\pi}{2} + 2k\pi \), where \( k \) is any integer, because the sine function has a period of \( 2\pi \).
03
Define the General Solution
Using the property of periodicity of the sine function, the general solution for \( x \) given \( \sin x = -1 \) is \( x = \frac{3\pi}{2} + 2k\pi \). This equation accounts for all angles that measure -1 for \( \sin x \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Sine Function
The sine function, denoted as \( \sin x \), is a fundamental concept in trigonometry. It describes the y-coordinate of a point on the unit circle for a given angle \( x \). When you analyze the sine function, it's important to understand that it can take values ranging from -1 to 1.
Here is how the sine function works:
Here is how the sine function works:
- The sine of an angle is the vertical coordinate of the corresponding point on the unit circle.
- \( \sin(0) = 0 \), since at angle 0, the y-coordinate is 0.
- \( \sin(\pi/2) = 1 \), at this angle, the y-coordinate reaches its maximum value (the top of the circle).
- \( \sin(\pi) = 0 \), curving back to the x-axis.
- \( \sin(3\pi/2) = -1 \), where the y-coordinate reaches its lowest value (the bottom of the circle).
Unit Circle
The unit circle is a circle with a radius of one, centered at the origin of a coordinate plane. It's an essential tool in trigonometry for understanding angles and their corresponding sine and cosine values.
In the context of the unit circle:
In the context of the unit circle:
- The unit circle helps to visualize the trigonometric functions and their properties.
- Each point on the unit circle corresponds to an angle measure, where the x-coordinate is the cosine and the y-coordinate is the sine of that angle.
- For example, the point \((0, -1)\) represents \(3\pi/2\) radians, where \(\sin(3\pi/2) = -1\).
Periodicity
Periodicity in trigonometry refers to the repeating nature of sine, cosine, and other trigonometric functions.
Understanding periodicity involves several key points:
Understanding periodicity involves several key points:
- The sine function has a periodicity of \(2\pi\), meaning that the function repeats its values every \(2\pi\) interval.
- This property is crucial for finding all solutions to trigonometric equations, as it allows us to express solutions in a recurring pattern.
- For example, the general solution for \(\sin x = -1\) is \(x = \frac{3\pi}{2} + 2k\pi\), where \(k\) is an integer. The term \(2k\pi\) accounts for each full rotation of the circle, returning to an angle where \(\sin x\) is again -1.