// Numbas version: exam_results_page_options {"name": "Helge's copy of Differentiation: Product rule", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"ungrouped_variables": ["a", "b", "s2", "s1", "m", "n"], "parts": [{"scripts": {}, "steps": [{"scripts": {}, "prompt": "

The product rule says that if $u$ and $v$ are functions of $x$ then
\\[\\simplify[std]{Diff(u * v,x,1) = u * Diff(v,x,1) + v * Diff(u,x,1)}\\]

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$\\simplify[std]{f(x) = sin({b}x + {a}) * e ^ ({n} * x)}$

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$\\displaystyle \\frac{df}{dx}=\\;$[[0]]

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Click on Show steps for more information, you will not lose any marks by doing  so.

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31/07/2012:

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Checked calculation.

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Added tags.

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Allowed no penalty on looking at Show steps.

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Differentiate $ \\sin(ax+b) e ^ {nx}$.

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The product rule says that if $u$ and $v$ are functions of $x$ then
\\[\\simplify[std]{Diff(u * v,x,1) = u * Diff(v,x,1) + v * Diff(u,x,1)}\\]

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For this example:

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\\[\\simplify[std]{u = sin({a} + {b} * x)}\\Rightarrow \\simplify[std]{Diff(u,x,1) = {b} * cos({a} + {b} * x)}\\]

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\\[\\simplify[std]{v = e ^ ({n} * x)} \\Rightarrow \\simplify[std]{Diff(v,x,1) = {n} * e ^ ({n} * x)}\\]

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Hence on substituting into the product rule above we get:

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\\[\\begin{eqnarray*}\\frac{df}{dx} &=& \\simplify[std]{{b} * cos({a} + {b} * x) * e ^ ({n} * x) + {n} * sin({a} + {b} * x) * e ^ ({n} * x)}\\\\\n\t \n\t &=&\\simplify[std]{({b}cos({a}+{b}x)+{n}sin({a}+{b}x))e^({n}x)}\n\t \n\t \\end{eqnarray*}\\]

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Differentiate the following function $f(x)$ using the product rule.

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