Chapter 7: Problem 83
Find the derivative of \(y\) with respect to the given independent variable. \begin{equation}y=3^{\log _{2} t}\end{equation}
Short Answer
Expert verified
The derivative is \( \frac{dy}{dt} = \frac{3^{\log _{2} t} \ln 3}{t \ln 2} \).
Step by step solution
01
Identify the function form
The given function is in the form \( y = a^{u} \), where \( a = 3 \) and \( u = \log_{2} t \). This indicates it's an exponential function with base 3 and exponent \( \log_{2} t \).
02
Apply the derivative of an exponential function
For a function of the form \( y = a^u \), the derivative \( \frac{dy}{dt} \) is given by \( \frac{dy}{du} \cdot \frac{du}{dt} \), where \( \frac{dy}{du} = a^{u} \ln a \).
03
Find du/dt
First, calculate \( \frac{du}{dt} \). Since \( u = \log_{2} t \), it can be rewritten using the change of base formula: \( u = \frac{\ln t}{\ln 2} \). Thus, \( \frac{du}{dt} = \frac{1}{t \ln 2} \) using the derivative of \( \ln t \), which is \( \frac{1}{t} \).
04
Combine results to find dy/dt
Combine the results: use \( \frac{dy}{du} = 3^{\log_{2} t} \ln 3 \) and \( \frac{du}{dt} = \frac{1}{t \ln 2} \). Therefore, \( \frac{dy}{dt} = 3^{\log _{2} t} \ln 3 \cdot \frac{1}{t \ln 2} \), simplify to \( \frac{dy}{dt} = \frac{3^{\log _{2} t} \ln 3}{t \ln 2} \).
05
Simplify the result (optional)
Further simplification is not required as \( \frac{dy}{dt} = \frac{3^{\log _{2} t} \ln 3}{t \ln 2} \) is in a simplified form, expressing the derivative explicitly.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Function
An exponential function is a type of mathematical function where a constant base is raised to a variable exponent. In the exercise, the function is given as \( y = 3^{\log_{2} t} \).
- Here, the constant base is \( 3 \) and the variable exponent is \( \log_{2} t \).
- The value of the base, \( a \), is crucial because it defines the growth rate of the function; larger bases grow faster.
- Exponential functions are commonly used to model growth processes, such as population growth or compound interest, where quantities increase rapidly over time.
Logarithmic Differentiation
Logarithmic differentiation is a technique used to differentiate functions where the standard rules of differentiation are cumbersome. It's particularly useful when dealing with complex or nested exponential functions.
In the example function \( y = 3^{\log_{2} t} \), logarithmic differentiation helps to iterate through the layers of functions.
In the example function \( y = 3^{\log_{2} t} \), logarithmic differentiation helps to iterate through the layers of functions.
- First, take the natural logarithm on both sides: \( \ln y = \ln (3^{\log_{2} t}) \).
- Use logarithmic identities to simplify: \( \ln y = \log_{2} t \cdot \ln 3 \).
- This allows the identification and separation of the exponent function, making the differentiation easier to execute step by step.
Change of Base Formula
The change of base formula is a mathematical technique enabling the conversion of logarithms from one base to another. It states: \[ \log_b a = \frac{\ln a}{\ln b} \]This formula is extremely useful when working with logarithms in derivatives, as it simplifies the differentiation process.
In the given exercise, \( u = \log_{2} t \), we employ this formula by changing it to natural logarithms as follows:
In the given exercise, \( u = \log_{2} t \), we employ this formula by changing it to natural logarithms as follows:
- Rewrite \( \log_{2} t = \frac{\ln t}{\ln 2} \).
- This manipulation converts base 2 logarithms into natural logarithms, which are easier to differentiate due to well-known derivative rules.
- This conversion is crucial for calculating \( \frac{du}{dt} \) because the derivative of \( \ln t \) is simply \( \frac{1}{t} \).