Problem 11 - Contemporary Precalculus

Question

Translate the given logarithmic statement into an equivalent exponential statement. $$\ln .01=-4.6052$$

Step-by-Step Solution

Answer

Question: Convert the logarithmic equation $\ln .01=-4.6052$ into an equivalent exponential equation. Answer: The equivalent exponential equation is $e^{-4.6052} = 0.01$.

Step 1: Identify the logarithmic equation

The given logarithmic equation is: $$\ln .01=-4.6052$$ Now, we need to convert this into an equivalent exponential equation.

Step 2: Convert the logarithmic equation into an exponential equation

Recall that the logarithm to the base e (the natural logarithm) can be defined as: $$\ln x=y \iff e^y=x$$ In our case, we have: $$\ln 0.01 = -4.6052$$ So, applying the definition, we can rewrite the equation as: $$e^{-4.6052} = 0.01$$ That's our exponential equation.

Key Concepts

Natural Logarithm

The natural logarithm is a special type of logarithm that is denoted as \(\ln x\). It's the power to which the number \(e\), known as Euler's number, approximately equal to 2.718281, must be raised to obtain the value \(x\). In other words, if \(\ln x = y\), then the number \(e\) raised to the power of \(y\) gives \(x\). This relationship is fundamental for converting a logarithmic statement into an exponential one. The given exercise displays how a natural logarithm that equates to a negative number can reflect the inverse exponential relationship where \(e\) is raised to a negative power, indicating division or a fraction in the exponential form.

For example, in the step-by-step solution, \(\ln 0.01 = -4.6052\) corresponds to the exponential equation \(e^{-4.6052} = 0.01\). Understanding the natural logarithm is essential in various fields including mathematics, physics, and engineering, as it describes growth processes and is pivotal in solving problems involving continuous compound interest, to name a few applications.

Exponential Equations

Exponential equations involve variables located in the exponent. In general, an exponential equation can be written as \(a^x = b\), where \(a\) is the base and \(b\) is the result of raising \(a\) to the power \(x\). To solve for \(x\), one often takes the logarithm of both sides of the equation which allows the variable in the exponent to be brought down as a coefficient. This is an essential technique because it transforms the exponential equation into a form that is easier to handle algebraically.

In the context of the exercise, converting the natural logarithm to the equivalent exponential form simplifies understanding of the relationship between the number \(e\) and any other number. This is particularly handy when dealing with continuous processes, like population growth or radioactive decay, where exponential equations are used to model such phenomena.

Logarithm Properties

Logarithms have specific properties that make them useful tools in solving mathematical problems. These include:

• The Product Rule: \(\ln(xy) = \ln(x) + \ln(y)\), which means the logarithm of a product is equal to the sum of the logarithms.
• The Quotient Rule: \(\ln\left(\frac{x}{y}\right) = \ln(x) - \ln(y)\), which states the logarithm of a quotient is the difference of the logarithms.
• The Power Rule: \(\ln(x^n) = n\ln(x)\), indicating that the logarithm of a number raised to a power is that power times the logarithm of the number.

These properties are instrumental in simplifying complex logarithmic expressions and solving logarithmic equations. A prime application, as seen in the exercise, is switching between logarithmic and exponential forms to find solutions. By harnessing these properties, students can more easily understand the inverse relationship between logarithms and exponents which is key to solving a wide array of mathematical problems, particularly in algebra and calculus.