Please login to create an exam or a quiz.
Find the derivative of \(\displaystyle y = \frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}}\)
Taking the natural logarithm of both sides of the equation and expanding the right hand side gives: \begin{equation*}\ln(y) = \ln{\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right)} \end{equation*} Expanding the right hand side using the product and quotient properties of logarithms gives: \begin{equation*}\ln(y) = 3 \ln{\left(x + 7 \right)}- x - 2 \ln{\left(- x - 6 \right)} - 3 \ln{\left(\cos{\left(x \right)} \right)} \end{equation*} Taking the derivative on both sides of the equation yields: \begin{equation*}\frac{y'}{y} = \frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6} \end{equation*} Solving for \(\displaystyle y'\) and substituting out y using the original equation gives \begin{equation*}y' = \left(\frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) \end{equation*} Using some Trigonometric identities to simplify gives \begin{equation*}y' = \left(\frac{3}{x + 7}3 \tan{\left(x \right)} - 1 + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) \end{equation*}
\begin{question}Find the derivative of $y = \frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}}$ \soln{9cm}{Taking the natural logarithm of both sides of the equation and expanding the right hand side gives: \begin{equation*}\ln(y) = \ln{\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right)} \end{equation*} Expanding the right hand side using the product and quotient properties of logarithms gives: \begin{equation*}\ln(y) = 3 \ln{\left(x + 7 \right)}- x - 2 \ln{\left(- x - 6 \right)} - 3 \ln{\left(\cos{\left(x \right)} \right)} \end{equation*} Taking the derivative on both sides of the equation yields: \begin{equation*}\frac{y'}{y} = \frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6} \end{equation*} Solving for $y'$ and substituting out y using the original equation gives \begin{equation*}y' = \left(\frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) \end{equation*} Using some Trigonometric identities to simplify gives \begin{equation*}y' = \left(\frac{3}{x + 7}3 \tan{\left(x \right)} - 1 + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) \end{equation*} } \end{question}
\documentclass{article} \usepackage{tikz} \usepackage{amsmath} \usepackage[margin=2cm]{geometry} \usepackage{tcolorbox} \newcounter{ExamNumber} \newcounter{questioncount} \stepcounter{questioncount} \newenvironment{question}{{\noindent\bfseries Question \arabic{questioncount}.}}{\stepcounter{questioncount}} \renewcommand{\labelenumi}{{\bfseries (\alph{enumi})}} \newif\ifShowSolution \newcommand{\soln}[2]{% \ifShowSolution% \noindent\begin{tcolorbox}[colframe=blue,title=Solution]#2\end{tcolorbox}\else% \vspace{#1}% \fi% }% \newcommand{\hideifShowSolution}[1]{% \ifShowSolution% % \else% #1% \fi% }% \everymath{\displaystyle} \ShowSolutiontrue \begin{document}\begin{question}(10pts) The question goes here! \soln{9cm}{The solution goes here.} \end{question}\end{document}
<p> <p>Find the derivative of <img class="equation_image" title=" \displaystyle y = \frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} " src="/equation_images/%20%5Cdisplaystyle%20y%20%3D%20%5Cfrac%7B%5Cleft%28x%20%2B%207%5Cright%29%5E%7B3%7D%20e%5E%7B-%20x%7D%7D%7B%5Cleft%28-%20x%20-%206%5Cright%29%5E%7B2%7D%20%5Ccos%5E%7B3%7D%7B%5Cleft%28x%20%5Cright%29%7D%7D%20" alt="LaTeX: \displaystyle y = \frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} " data-equation-content=" \displaystyle y = \frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} " /> </p> </p>
<p> <p>Taking the natural logarithm of both sides of the equation and expanding the right hand side gives:
<img class="equation_image" title=" \ln(y) = \ln{\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right)} " src="/equation_images/%20%5Cln%28y%29%20%3D%20%5Cln%7B%5Cleft%28%5Cfrac%7B%5Cleft%28x%20%2B%207%5Cright%29%5E%7B3%7D%20e%5E%7B-%20x%7D%7D%7B%5Cleft%28-%20x%20-%206%5Cright%29%5E%7B2%7D%20%5Ccos%5E%7B3%7D%7B%5Cleft%28x%20%5Cright%29%7D%7D%20%5Cright%29%7D%20%20%20" alt="LaTeX: \ln(y) = \ln{\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right)} " data-equation-content=" \ln(y) = \ln{\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right)} " />
Expanding the right hand side using the product and quotient properties of logarithms gives:
<img class="equation_image" title=" \ln(y) = 3 \ln{\left(x + 7 \right)}- x - 2 \ln{\left(- x - 6 \right)} - 3 \ln{\left(\cos{\left(x \right)} \right)} " src="/equation_images/%20%5Cln%28y%29%20%3D%203%20%5Cln%7B%5Cleft%28x%20%2B%207%20%5Cright%29%7D-%20x%20-%202%20%5Cln%7B%5Cleft%28-%20x%20-%206%20%5Cright%29%7D%20-%203%20%5Cln%7B%5Cleft%28%5Ccos%7B%5Cleft%28x%20%5Cright%29%7D%20%5Cright%29%7D%20%20%20" alt="LaTeX: \ln(y) = 3 \ln{\left(x + 7 \right)}- x - 2 \ln{\left(- x - 6 \right)} - 3 \ln{\left(\cos{\left(x \right)} \right)} " data-equation-content=" \ln(y) = 3 \ln{\left(x + 7 \right)}- x - 2 \ln{\left(- x - 6 \right)} - 3 \ln{\left(\cos{\left(x \right)} \right)} " />
Taking the derivative on both sides of the equation yields:
<img class="equation_image" title=" \frac{y'}{y} = \frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6} " src="/equation_images/%20%5Cfrac%7By%27%7D%7By%7D%20%3D%20%5Cfrac%7B3%20%5Csin%7B%5Cleft%28x%20%5Cright%29%7D%7D%7B%5Ccos%7B%5Cleft%28x%20%5Cright%29%7D%7D%20-%201%20%2B%20%5Cfrac%7B3%7D%7Bx%20%2B%207%7D%20%2B%20%5Cfrac%7B2%7D%7B-%20x%20-%206%7D%20%20%20" alt="LaTeX: \frac{y'}{y} = \frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6} " data-equation-content=" \frac{y'}{y} = \frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6} " />
Solving for <img class="equation_image" title=" \displaystyle y' " src="/equation_images/%20%5Cdisplaystyle%20y%27%20" alt="LaTeX: \displaystyle y' " data-equation-content=" \displaystyle y' " /> and substituting out y using the original equation gives
<img class="equation_image" title=" y' = \left(\frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) " src="/equation_images/%20y%27%20%3D%20%5Cleft%28%5Cfrac%7B3%20%5Csin%7B%5Cleft%28x%20%5Cright%29%7D%7D%7B%5Ccos%7B%5Cleft%28x%20%5Cright%29%7D%7D%20-%201%20%2B%20%5Cfrac%7B3%7D%7Bx%20%2B%207%7D%20%2B%20%5Cfrac%7B2%7D%7B-%20x%20-%206%7D%5Cright%29%5Cleft%28%5Cfrac%7B%5Cleft%28x%20%2B%207%5Cright%29%5E%7B3%7D%20e%5E%7B-%20x%7D%7D%7B%5Cleft%28-%20x%20-%206%5Cright%29%5E%7B2%7D%20%5Ccos%5E%7B3%7D%7B%5Cleft%28x%20%5Cright%29%7D%7D%20%5Cright%29%20%20%20" alt="LaTeX: y' = \left(\frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) " data-equation-content=" y' = \left(\frac{3 \sin{\left(x \right)}}{\cos{\left(x \right)}} - 1 + \frac{3}{x + 7} + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) " />
Using some Trigonometric identities to simplify gives
<img class="equation_image" title=" y' = \left(\frac{3}{x + 7}3 \tan{\left(x \right)} - 1 + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) " src="/equation_images/%20y%27%20%3D%20%5Cleft%28%5Cfrac%7B3%7D%7Bx%20%2B%207%7D3%20%5Ctan%7B%5Cleft%28x%20%5Cright%29%7D%20-%201%20%2B%20%5Cfrac%7B2%7D%7B-%20x%20-%206%7D%5Cright%29%5Cleft%28%5Cfrac%7B%5Cleft%28x%20%2B%207%5Cright%29%5E%7B3%7D%20e%5E%7B-%20x%7D%7D%7B%5Cleft%28-%20x%20-%206%5Cright%29%5E%7B2%7D%20%5Ccos%5E%7B3%7D%7B%5Cleft%28x%20%5Cright%29%7D%7D%20%5Cright%29%20%20%20" alt="LaTeX: y' = \left(\frac{3}{x + 7}3 \tan{\left(x \right)} - 1 + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) " data-equation-content=" y' = \left(\frac{3}{x + 7}3 \tan{\left(x \right)} - 1 + \frac{2}{- x - 6}\right)\left(\frac{\left(x + 7\right)^{3} e^{- x}}{\left(- x - 6\right)^{2} \cos^{3}{\left(x \right)}} \right) " />
</p> </p>