Chapter 5: Problem 75
Determine whether the function is even, odd, or neither. $$f(x)=\sin x \cos x$$
Short Answer
Expert verified
The function is odd.
Step by step solution
01
Define Properties of Even and Odd Functions
For a function to be even, it must satisfy the condition \( f(-x) = f(x) \) for all \( x \). For a function to be odd, the condition \( f(-x) = -f(x) \) must hold true for all \( x \). If neither condition is met, the function is neither even nor odd.
02
Substitute -x into the Function
Substitute \(-x\) into the function: \( f(-x) = \sin(-x) \cdot \cos(-x) \). Recall that \( \sin(-x) = -\sin(x) \) and \( \cos(-x) = \cos(x) \). Therefore, \( f(-x) = -\sin(x) \cdot \cos(x) \).
03
Compare \(f(-x)\) with \(f(x)\)
From step 2, we have \( f(-x) = -\sin(x) \cdot \cos(x) \) and the original function \( f(x) = \sin(x) \cdot \cos(x) \).We observe that\( f(-x) = -f(x) \).
04
Conclude the Nature of the Function
Since \( f(-x) = -f(x) \), the function \( f(x) = \sin(x) \cos(x) \) meets the condition for an odd function. Therefore, the function is odd.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Even and Odd Functions
Understanding whether a function is even, odd, or neither is essential in precalculus. This concept helps in determining the symmetry of the function's graph. Here’s how you identify these functions:
- Even Functions: A function is even if for every x, the equation \( f(-x) = f(x) \) holds true. This means that the graph of an even function is symmetrical about the y-axis.
- Odd Functions: Conversely, a function is odd if for all x, \( f(-x) = -f(x) \) is satisfied. An odd function’s graph has rotational symmetry about the origin.
- Neither: If a function does not satisfy either condition, it is considered neither even nor odd.
Trigonometric Functions
Trigonometric functions like sine, cosine, and tangent are fundamental to mathematics, describing periodic phenomena.
- Sine Function: Denoted as \( \sin(x) \), it is an odd function. This means that \( \sin(-x) = -\sin(x) \).
- Cosine Function: Represented as \( \cos(x) \), it is an even function since \( \cos(-x) = \cos(x) \).
- Tangent Function: Known as \( \tan(x) \), is an odd function, similar to sine.
Function Properties
Function properties aid in understanding more about a function's behavior without graphing it. These properties extend beyond even and odd characteristics:
- Periodicity: Many trigonometric functions, like sine and cosine, repeat their values after a certain interval. This is the function’s period. For instance, \( \sin(x) \) and \( \cos(x) \) have periods of \( 2\pi \).
- Symmetry: Knowing if a function is even or odd can help quickly identify symmetry, which simplifies graphing and understanding the function’s graph.
- Amplitude and Phase Shift: In trigonometric contexts, the amplitude indicates the height of function peaks, while phase shift describes horizontal shifts on a graph. Functions like \( \sin(x) \) often have these characteristics.