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+%%
+%% This is file `implicit.tex',
+%% generated with the docstrip utility.
+%%
+%% The original source files were:
+%%
+%% probsoln.dtx (with options: `implicit.tex,package')
+%% Copyright (C) 2006 Nicola Talbot, all rights reserved.
+%% If you modify this file, you must change its name first.
+%% You are NOT ALLOWED to distribute this file alone. You are NOT
+%% ALLOWED to take money for the distribution or use of either this
+%% file or a changed version, except for a nominal charge for copying
+%% etc.
+%% \CharacterTable
+%% {Upper-case \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
+%% Lower-case \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
+%% Digits \0\1\2\3\4\5\6\7\8\9
+%% Exclamation \! Double quote \" Hash (number) \#
+%% Dollar \$ Percent \% Ampersand \&
+%% Acute accent \' Left paren \( Right paren \)
+%% Asterisk \* Plus \+ Comma \,
+%% Minus \- Point \. Solidus \/
+%% Colon \: Semicolon \; Less than \<
+%% Equals \= Greater than \> Question mark \?
+%% Commercial at \@ Left bracket \[ Backslash \\
+%% Right bracket \] Circumflex \^ Underscore \_
+%% Grave accent \` Left brace \{ Vertical bar \|
+%% Right brace \} Tilde \~}
+
+\newproblem{imd:circ}{%
+Find the gradient of the unit circle ($x^2 + y^2 = 1$).}{%
+Differentiating with respect to $x$ gives:
+\begin{eqnarray*}
+2x + 2y\frac{dy}{dx} & = & 0\\
+\frac{dy}{dx} & = & \frac{-2x}{2y}\\
+ & = & \frac{-x}{\sqrt{1-x^2}}.
+\end{eqnarray*}}
+
+\newproblem{imd:ysq:xcuov2mx}{%
+Find $\frac{dy}{dx}$, given
+\begin{displaymath}
+y^2 = \frac{x^3}{2-x}
+\end{displaymath}}{%
+Differentiating both sides w.r.t.\ $x$:
+\begin{eqnarray*}
+2y\frac{dy}{dx} & = & \frac{(2-x)3x^2 - x^3(-1)}{(2-x)^2}\\
+ & = & \frac{3x^2(2-x) + x^3}{(2-x)^2}\\
+ & = & \frac{6x^2 - 3x^3 + x^3}{(2-x)^2}\\
+ & = & \frac{6x^2-2x^3}{(2-x)^2}\\
+ & = & 2x^2\frac{3-x}{(2-x)^2}
+\end{eqnarray*}
+Therefore
+\begin{displaymath}
+y\frac{dy}{dx} = x^2\frac{3-x}{(2-x)^2}
+\end{displaymath}}
+
+\newproblem{imd:exy:IIxay}{%
+Differentiate w.r.t.\ $x$:
+\begin{displaymath}
+e^{xy} = 2x + y
+\end{displaymath}}{%
+Differentiating both sides w.r.t.\ $x$:
+\begin{eqnarray*}
+e^{xy}(1y + x\frac{dy}{dx}) & = & 2 + \frac{dy}{dx}\\
+xe^{xy}\frac{dy}{dx} - \frac{dy}{dx} & = & 2 - ye^{xy} \\
+\frac{dy}{dx}(xe^{xy}-1) & = & 2 - ye^{xy}\\
+\frac{dy}{dx} & = & \frac{2-ye^{xy}}{xe^{xy}-1}
+\end{eqnarray*}}
+\endinput
+%%
+%% End of file `implicit.tex'.