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Evaluate the following definite integral correct to three decimal places:

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\\(\\int_\\var{a}^\\var{b}\\var{m}sin^\\var{n}(\\var{k}t)cos^3(\\var{k}t)dt\\)

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\\(\\int_\\var{a}^\\var{b}\\var{m}sin^\\var{n}(\\var{k}t)cos^3(\\var{k}t)dt\\)

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Let \\(u=sin(\\var{k}t)\\)  \\(\\implies \\frac{du}{dt}=\\var{k}cos(\\var{k}t)\\)

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\\(\\frac{1}{\\var{k}cos(\\var{k}t)}du=dt\\)

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\\(\\int_\\var{a}^\\var{b}\\var{m}u^\\var{n}cos^3(\\var{k}t)\\frac{1}{\\var{k}cos(\\var{k}t)}du\\)

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\\(=\\int_\\var{a}^\\var{b}\\frac{\\var{m}}{\\var{k}}u^\\var{n}cos^2(\\var{k}t)du\\)

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\\(but\\)  \\(cos^2(\\var{k}t)=1-sin^2(\\var{k}t)=1-u^2\\)

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\\(=\\int_\\var{a}^\\var{b}\\frac{\\var{m}}{\\var{k}}u^\\var{n}(1-u^2)du\\)

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\\(=\\int_\\var{a}^\\var{b}\\frac{\\var{m}}{\\var{k}}u^\\var{n}-\\frac{\\var{m}}{\\var{k}}u^\\simplify{{n}+2}du\\)

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\\(=\\frac{\\var{m}}{\\var{k}}\\frac{u^{\\simplify{{n}+1}}}{\\simplify{{n}+1}}-\\frac{\\var{m}}{\\var{k}}\\frac{u^{\\simplify{{n}+3}}}{\\simplify{{n}+3}}\\)

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\\(=\\frac{\\var{m}}{\\simplify{{k}*({n}+1)}}sin^{\\simplify{{n}+1}}(\\var{k}t)-\\frac{\\var{m}}{\\simplify{{k}*({n}+3)}}sin^{\\simplify{{n}+3}}(\\var{k}t)\\Big|_\\var{a}^\\var{b}\\)

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\\(=\\frac{\\var{m}}{\\simplify{{k}*({n}+1)}}\\left(sin^{\\simplify{{n}+1}}(\\simplify{{k}*{b}})-sin^{\\simplify{{n}+1}}(\\simplify{{k}*{a}})\\right)-\\frac{\\var{m}}{\\simplify{{k}*({n}+3)}}\\left(sin^{\\simplify{{n}+3}}(\\simplify{{k}*{b}})-sin^{\\simplify{{n}+3}}(\\simplify{{k}*{a}})\\right)\\)

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\\(=\\simplify{{m}/({k}*({n}+1))}*\\left(\\simplify{(sin({{k}*{b}}))}^\\simplify{{{{n}+1}}}-\\simplify{(sin({{k}*{a}}))}^\\simplify{{{{n}+1}}}\\right)-\\simplify{{m}/({k}*({n}+3))}*\\left(\\simplify{(sin({{k}*{b}}))}^\\simplify{{{{n}+3}}}-\\simplify{(sin({{k}*{a}}))}^\\simplify{{{{n}+3}}}\\right)\\)

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\\(Answer =\\) [[0]]

", "showFeedbackIcon": true, "showCorrectAnswer": true, "scripts": {}, "variableReplacements": [], "variableReplacementStrategy": "originalfirst"}], "type": "question", "contributors": [{"name": "Frank Doheny", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/789/"}]}]}], "contributors": [{"name": "Frank Doheny", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/789/"}]}