// Numbas version: exam_results_page_options {"name": "Differentiate product of binomial, trig, and exponential", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"variable_groups": [], "variables": {"s1": {"templateType": "anything", "group": "Ungrouped variables", "definition": "random(1,-1)", "description": "", "name": "s1"}, "n": {"templateType": "anything", "group": "Ungrouped variables", "definition": "s2*random(2..5)", "description": "", "name": "n"}, "b": {"templateType": "anything", "group": "Ungrouped variables", "definition": "s1*random(2..9)", "description": "", "name": "b"}, "m": {"templateType": "anything", "group": "Ungrouped variables", "definition": "random(2..8)", "description": "", "name": "m"}, "a": {"templateType": "anything", "group": "Ungrouped variables", "definition": "random(1..9)", "description": "", "name": "a"}, "s2": {"templateType": "anything", "group": "Ungrouped variables", "definition": "random(1,-1)", "description": "", "name": "s2"}}, "ungrouped_variables": ["a", "b", "s2", "s1", "m", "n"], "question_groups": [{"pickingStrategy": "all-ordered", "questions": [], "name": "", "pickQuestions": 0}], "name": "Differentiate product of binomial, trig, and exponential", "functions": {}, "showQuestionGroupNames": false, "parts": [{"stepsPenalty": 0, "scripts": {}, "gaps": [{"answer": "{b}x * cos({b} * x+{a}) + ({n}x+{m}) * sin({b} * x+{a})", "showCorrectAnswer": true, "vsetrange": [0, 1], "checkingaccuracy": 0.001, "checkvariablenames": false, "expectedvariablenames": [], "showpreview": true, "checkingtype": "absdiff", "scripts": {}, "type": "jme", "answersimplification": "std", "marks": 3, "vsetrangepoints": 5}], "type": "gapfill", "prompt": "\n
$\\simplify[std]{f(x) = x^{m}sin({b}x + {a}) * e ^ ({n} * x)}$
\nThe answer is of the form:
\n$\\displaystyle \\frac{df}{dx}= \\simplify[std]{x^{m-1}e^({n}x)g(x)}$ for a function $g(x)$. You have to find $g(x)$
\n$g(x)=\\;$[[0]]
\nif you input a function of the form $xf(x)$ where $f(x)$ is a function, then you must input it as $x*f(x)$ with * for multiplication e.g. input $x*\\sin(ax+b)$ and not $xsin(ax+b)$.
\nClick on Show steps for more information, you will not lose any marks by doing so.
\n ", "steps": [{"type": "information", "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)}\\]
Differentiate the following function $f(x)$ using the product rule.
", "tags": ["checked2015", "MAS1601"], "rulesets": {"std": ["all", "!collectNumbers", "fractionNumbers"], "surdf": [{"result": "(sqrt(b)*a)/b", "pattern": "a/sqrt(b)"}]}, "preamble": {"css": "", "js": ""}, "type": "question", "metadata": {"notes": "\n \t\t31/07/2012:
\n \t\tChecked calculation.
\n \t\tAdded tags.
\n \t\tAllowed no penalty on looking at Show steps.
\n \t\tCorrected occurences of the form xsin and xcos to x*sin, x*cos.
\n \t\tIncluded message warning about the input of functions of the form xsin etc.
\n \t\tShow steps needs to be resolved. Now resolved.
\n \t\t", "licence": "Creative Commons Attribution 4.0 International", "description": "Differentiate $f(x)=x^{m}\\sin(ax+b) e^{nx}$.
\nThe answer is of the form:
$\\displaystyle \\frac{df}{dx}= x^{m-1}e^{nx}g(x)$ for a function $g(x)$.
Find $g(x)$.
"}, "variablesTest": {"condition": "", "maxRuns": 100}, "advice": "\nThe 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)}\\]
For this example:
\\[\\simplify[std]{u = x^{m}} \\Rightarrow \\simplify[std]{Diff(u,x,1) = {m}x^{m-1}}\\]
\\[\\simplify[std]{v = sin({b} * x+{a})e^({n}x)}\\Rightarrow \\simplify[std]{Diff(v,x,1) = {b} * cos({b} * x+{a})e^({n}x)+{n}sin({b}x+{a})e^({n}x)}\\]
\nHence on substituting into the product rule above we get:
\n\\[\\begin{eqnarray*}\\frac{df}{dx} &=& \\simplify[std]{{m}x^{m-1}sin({b} * x+{a})e^({n}x)+x^{m}({b} * cos({b} * x+{a}) * e ^ ({n} * x) + {n} * sin({b} * x+{a}) * e ^ ({n} * x))}\\\\ &=&\\simplify[std]{x^{m-1}e^({n}x)({b}x*cos({b}x+{a})+{n}x*sin({b}x+{a})+{m}sin({b}x+{a}))}\\\\ &=&\\simplify[std]{x^{m-1}e^({n}x)({b}x*cos({b}x+{a})+({n}x+{m})*sin({b}x+{a}))} \\end{eqnarray*}\\]
Hence $g(x)=\\simplify[std]{{b}x*cos({b}x+{a})+({n}x+{m})*sin({b}x+{a})}$