Chapter 4: Problem 53
Find the linear approximation \(L(x)\) to \(y=f(x)\) near \(x=a\) for the function. \(f(x)=\sin x, a=\frac{\pi}{2}\)
Short Answer
Expert verified
The linear approximation is \(L(x) = 1\).
Step by step solution
01
Calculate the Derivative
The first step is to find the derivative of the function \(f(x) = \sin x\). The derivative of \(\sin x\) with respect to \(x\) is \(\cos x\). Therefore, \(f'(x) = \cos x\).
02
Evaluate Function and Derivative at a.
Evaluate both the function \(f(x)\) and its derivative \(f'(x)\) at \(x = a\), where \(a = \frac{\pi}{2}\). First, find \(f\left(\frac{\pi}{2}\right) = \sin\left(\frac{\pi}{2}\right) = 1\). Next, calculate \(f'\left(\frac{\pi}{2}\right) = \cos\left(\frac{\pi}{2}\right) = 0\).
03
Write the Formula for Linear Approximation
The linear approximation \(L(x)\) of the function near \(x = a\) is given by: \(L(x) = f(a) + f'(a)(x - a)\).
04
Substitute Values into Linear Approximation Formula
Substitute \(f(a) = 1\), \(f'(a) = 0\), and \(a = \frac{\pi}{2}\) into the linear approximation formula: \(L(x) = 1 + 0 \cdot (x - \frac{\pi}{2})\).
05
Simplify the Expression
Simplify the expression \(L(x) = 1 + 0 \cdot (x - \frac{\pi}{2})\) to get \(L(x) = 1\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Derivative of Sine Function
To understand the linear approximation of a function, we must first know how to find its derivative. For a sine function, like \( f(x) = \sin x \), the derivative tells us how the function changes at any point along its curve. The derivative of \( \sin x \) is \( \cos x \).
- The derivative \( \cos x \) is a result of differentiating \( \sin x \).
- This derivative is essential as it helps in finding the slope of the function at any point.
Evaluate Derivative at a Point
Once we have a derivative, we need to evaluate it at a specific point. Evaluating the derivative at a given point tells us the exact rate of change of the function at that point. For example, if we have \( f(x) = \sin x \) and we want to evaluate at \( a = \frac{\pi}{2} \):
- First, we calculate \( f\left(\frac{\pi}{2}\right) = \sin\left(\frac{\pi}{2}\right) = 1\).
- Next, we find \( f'\left(\frac{\pi}{2}\right) = \cos\left(\frac{\pi}{2}\right) = 0\).
Linearization Formula
With both the function value and the derivative evaluated at a point, we apply the linearization formula. The linear approximation formula is a perfect tool to understand how the function behaves near a specific point. The formula is:
\[ L(x) = f(a) + f'(a)(x - a) \]
\[ L(x) = f(a) + f'(a)(x - a) \]
- \(L(x)\) is the linear approximation of \(f(x)\) near \(x = a\).
- In our case, substitute \( f(a) = 1 \), \( f'(a) = 0 \), and \(a = \frac{\pi}{2}\).
Simplifying Expressions
The last step in finding the linear approximation is to simplify the expression derived from the linearization formula. Often, simplifying can turn a complex-looking expression into a simple one, making it easier to interpret. Based on our calculation:
- Substitute the values: \(L(x) = 1 + 0 \cdot (x - \frac{\pi}{2})\).
- Simplify to \(L(x) = 1\).