Chapter 9: Problem 65
Solve each equation. Express all answers to four decimal places. $$ \ln x=-3.71 $$
Short Answer
Expert verified
The solution is \( x \approx 0.0246 \).
Step by step solution
01
Recall the Definition of a Natural Logarithm
The natural logarithm function, denoted as \( \ln(x) \), is the inverse of the exponential function \( e^x \). This means that if \( y = \ln(x) \), then \( x = e^y \). We will use this property to solve the equation \( \ln x = -3.71 \).
02
Exponentiate Both Sides of the Equation
To isolate \( x \), exponentiate both sides using base \( e \). This transforms the equation from logarithmic to exponential form: \[ e^{\ln x} = e^{-3.71} \]Since \( e^{\ln x} = x \), this simplifies to:\[ x = e^{-3.71} \]
03
Calculate \( e^{-3.71} \) Using a Calculator
Use a scientific calculator to find the value of \( e^{-3.71} \). Entering \( -3.71 \) and then executing the exponential function \\( e^x \) will give the solution. Ensure your calculator is set to the appropriate mode for natural exponentiation. The result is approximately:\( x \approx 0.0245907 \)
04
Round the Result to Four Decimal Places
Round the calculated value of \( x \) to four decimal places as instructed. The number 0.0245907 rounded to four decimal places is:\( x \approx 0.0246 \)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Function
The exponential function is a fundamental mathematical function that grows rapidly. It is represented as \( e^x \), where \( e \) is a constant approximately equal to 2.71828. This function has unique properties, such as:
- Its rate of growth is proportional to its current value.
- It is continuous and differentiable, which means it's smooth and has a slope everywhere.
- It is one-to-one, meaning each input results in one unique output.
Inverse Functions
Inverse functions essentially reverse the effect of their corresponding functions. For any function \( f \), the inverse function, denoted as \( f^{-1} \), works by swapping the roles of the input and output. In mathematical terms, if \( y = f(x) \), then \( x = f^{-1}(y) \).The natural logarithm \( \ln(x) \) and the exponential function \( e^x \) are perfect examples of inverse functions:
- The natural logarithm finds which power the constant \( e \) must be raised to produce \( x \).
- The exponential function takes a logarithm result and returns the original base number.
Scientific Calculator Usage
Handling mathematical calculations in equations like \( e^{-3.71} \), a scientific calculator becomes an invaluable tool. Here's how to use it efficiently:Start by ensuring that your calculator is in "scientific mode," which allows access to functions like exponents. To calculate \( e^{-3.71} \):
- Enter \(-3.71\) into the calculator.
- Press the \( e^x \) button to apply the exponential function to this input value.
- The resulting display provides the calculated value, around 0.0245907 in our case.
- Lastly, if needed, round this to four decimal places for precision, resulting in 0.0246.