Advanced differentiation problems : Exercises

Introduction

To solve the following problems you will need to use everything you know about the differential operator. It will be particularly important to remember that the differential operator has the distributative property over addition, that the chain rule allows us to evaluate the differential of the function $f[u(x)]$ with respect to $x$ using: $$ \frac{\textrm{d}f}{\textrm{d}x} = \frac{\textrm{d}f}{\textrm{d}u} \frac{\textrm{d}u}{\textrm{d}x} $$ Last of all you will need to remember that the product rule can be used to calculate the differentials of products of functions such as $f(x) = u(x)v(x)$. The product rule states in this case that: $$ \frac{\textrm{d}f}{\textrm{d}x} = u \frac{\textrm{d}v}{\textrm{d}x} + v\frac{\textrm{d}u}{\textrm{d}x} $$

Example problems

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Problems for you to try

$y=x^3 \ln x - \frac{x^3}{3}$ $y = 2t\sin t - (t^2 - 2\cos t)$ $f(t) = \sin(t)\sin(t+\phi)$ $y = \frac{1+ \sqrt{z}}{1 - \sqrt{z} }$
$y = 5e^{-ax^2}$ $y = \sqrt{a^2 - x^2}$ $y = (3-2\sin(x))^5$

Problems for you to try

Find the derivative of the following function with respect to $y$: $$ f(y) = \frac{\int_a^b v(x) \exp\left( - \frac{\phi(y,x)}{2\sigma^2} \right) \textrm{d}x }{ \int_a^b \exp\left( - \frac{\phi(y,x)}{2\sigma^2} \right) \textrm{d}x } $$ Hint: $\frac{\partial \phi(y,x)}{\partial y} = \phi'(y,x)$

Contact Details

School of Mathematics and Physics,
Queen's University Belfast,
Belfast,
BT7 1NN

Email: g.tribello@qub.ac.uk
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