Chapter 12: Problem 37
Use a calculator to evaluate each expression to four decimal places. $$ e^{-4} $$
Short Answer
Expert verified
The value of \( e^{-4} \) to four decimal places is 0.0183.
Step by step solution
01
Understand the Expression
The expression we need to evaluate is the exponential function with a negative exponent: \( e^{-4} \). This means we are finding the reciprocal of \( e^4 \).
02
Use a Calculator for Calculation
Turn on your calculator and make sure it has the function for computing \( e \) or exponential calculations. Most scientific calculators have a dedicated button for \( e^x \).
03
Input the Expression
On the calculator, locate the button for raising \( e \) to a power, usually labeled as \( e^x \) or similar. Enter \(-4\) as the exponent, so input \( e^{-4} \).
04
Calculate
Press the equals button to perform the calculation. The calculator will provide the result for \( e^{-4} \).
05
Round the Result
Take the answer from the calculator and round it to four decimal places. For example, if the calculator shows 0.0183156, rounding it will give 0.0183.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Negative Exponents
Negative exponents might seem a bit tricky at first, but they're not as complicated as they appear. When you see a negative exponent, like in the expression \( e^{-4} \), it means you are dealing with the reciprocal of a positive exponent. For example, \( e^{-4} \) is the same as \( \frac{1}{e^4} \). This transformation is a crucial concept:
- Negative exponent indicates reciprocal.
- \( e^{-4} = \frac{1}{e^4} \).
- For any base \( a \), \( a^{-n} = \frac{1}{a^n} \).
Scientific Calculators
Scientific calculators are essential tools for dealing with exponential functions like \( e^x \), especially when the calculations involve negative exponents. A scientific calculator has functionalities to handle complex operations including exponential, logarithmic, and trigonometric calculations. Here’s how you can typically use them for an expression like \( e^{-4} \):
- Turn the calculator on and ensure it’s in the correct mode for scientific calculations.
- Locate the exponent function, often labeled as \( e^x \) or similar.
- Enter the base \( e \) and the exponent (-4) you wish to evaluate.
- Press the equals or execute button to calculate the result.
Rounding Decimals
Rounding decimals is a crucial skill, particularly when working on scientific tasks that demand precision. When you compute an expression like \( e^{-4} \) using a calculator, it might display a result such as 0.0183156. For consistency in results and clarity, especially in educational contexts, it’s often desirable to round to a specific number of decimal places. Here’s how you can round to four decimal places:
- Identify the fourth decimal place. In 0.0183156, this is 5.
- Look at the next decimal place (in this example, it is 1) to decide whether to round up or keep the number as it is.
- Since the number following the 4th decimal place is less than 5, you do not round up, so 0.0183156 becomes 0.0183 when rounded to four decimal places.