Chapter 7: Problem 129
Find the length of each curve. $$y=\frac{1}{2}\left(e^{x}+e^{-x}\right) \text { from } x=0 \text { to } x=1$$
Short Answer
Expert verified
The length of the curve is \( \frac{1}{2} \left( e - \frac{1}{e} \right) \).
Step by step solution
01
Write the Formula for Arc Length
The formula to find the length of a curve described by a function \( y = f(x) \) from \( x = a \) to \( x = b \) is given by:\[ L = \int_a^b \sqrt{1 + \left( \frac{dy}{dx} \right)^2} \, dx \]
02
Calculate the Derivative of the Function
Given the function \( y = \frac{1}{2} \left( e^x + e^{-x} \right) \).First, find the derivative, \( \frac{dy}{dx} \):\[ \frac{dy}{dx} = \frac{1}{2} \left( e^x - e^{-x} \right) \]
03
Plug the Derivative into the Arc Length Formula
Substitute \( \frac{dy}{dx} = \frac{1}{2} \left( e^x - e^{-x} \right) \) into the arc length formula:\[ L = \int_0^1 \sqrt{1 + \left( \frac{1}{2} \left( e^x - e^{-x} \right) \right)^2} \, dx \]
04
Simplify the Expression Under the Square Root
Simplify the expression under the square root:\[ \left( \frac{1}{2} (e^x - e^{-x}) \right)^2 = \frac{1}{4} (e^{2x} - 2 + e^{-2x}) \]Which means the integrand becomes:\[ \sqrt{1 + \frac{1}{4} (e^{2x} - 2 + e^{-2x})} = \sqrt{\frac{1}{2} (e^{2x} + e^{-2x})} \]
05
Substitute the Simplified Expression Back into the Integral
Now substitute the simplified expression back into the integral:\[ L = \int_0^1 \frac{1}{2} (e^x + e^{-x}) \, dx \]
06
Evaluate the Integral
This integral is straightforward to evaluate:\[ \int_0^1 \frac{1}{2} (e^x + e^{-x}) \, dx = \frac{1}{2} \left[ e^x - e^{-x} \right]_0^1 \]Calculate:\[ \frac{1}{2} \left[ (e^1 - e^{-1}) - (e^0 - e^{0}) \right] = \frac{1}{2} (e - \frac{1}{e} - 0) \]
07
Simplify the Final Expression
Finally, simplify to get the length:\[ L = \frac{1}{2} \left( e - \frac{1}{e} \right) \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Integral Calculus
Integral calculus is a core topic in mathematics that focuses on finding the total accumulation of quantities. One common use is finding the arc length of a curve. In our problem set, we calculated the arc length of the function \( y = \frac{1}{2}(e^x + e^{-x}) \) from \( x = 0 \) to \( x = 1 \).
- The arc length formula is crucial here: \( L = \int_a^b \sqrt{1 + \left( \frac{dy}{dx} \right)^2}\, dx \).
- This formula accounts for the derivative, \( \frac{dy}{dx} \), which affects the rate of change of the curve.
- Integrating this expression from \( x = 0 \) to \( x = 1 \) gives us the total length of the curve.
Derivative Calculation
Understanding derivatives is essential in calculus as they represent the rate of change of a function. In this problem, we first derive the given function \( y = \frac{1}{2} (e^x + e^{-x}) \).
- To find the derivative \( \frac{dy}{dx} \), apply the derivative rules for exponential functions. The result: \( \frac{dy}{dx} = \frac{1}{2} (e^x - e^{-x}) \).
- Derivatives provide a snapshot of how the curve slopes at any given point, enabling the calculation of arc length.
- Incorporating these derivatives into the arc length formula helps to portray the path a function traces more accurately.
Exponential Functions
Exponential functions, recognizable through their continuous growth or decay patterns, are pivotal in numerous real-world applications. Here, the function \( y = \frac{1}{2} (e^x + e^{-x}) \) incorporates both exponential growth \( e^x \) and decay \( e^{-x} \).
- Exponential functions are defined as \( y = a \cdot e^{kx} \) where \( e \) is a mathematical constant approximately equal to 2.71828.
- The base of the natural logarithm \( e \) aids in the simplification of growth and decay problems.
- In the given function, the terms \( e^x \) and \( e^{-x} \) represent growth and decay, respectively, impacting the curve's behavior and shape.