// Numbas version: exam_results_page_options {"name": "Contour integral of a complex function II", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"variable_groups": [], "variables": {"tol": {"templateType": "anything", "group": "Ungrouped variables", "definition": "0.001", "description": "", "name": "tol"}, "c1": {"templateType": "anything", "group": "Ungrouped variables", "definition": "random(1..4)", "description": "", "name": "c1"}, "v": {"templateType": "anything", "group": "Ungrouped variables", "definition": "precround(exp(-b1)*sin(c1),3)", "description": "", "name": "v"}, "b1": {"templateType": "anything", "group": "Ungrouped variables", "definition": "random(1..4)", "description": "", "name": "b1"}, "u": {"templateType": "anything", "group": "Ungrouped variables", "definition": "precround(exp(-a1)-exp(-b1)*cos(c1),3)", "description": "", "name": "u"}, "a1": {"templateType": "anything", "group": "Ungrouped variables", "definition": "random(1..4)", "description": "", "name": "a1"}}, "ungrouped_variables": ["a1", "u", "b1", "tol", "v", "c1"], "question_groups": [{"pickingStrategy": "all-ordered", "questions": [], "name": "", "pickQuestions": 0}], "name": "Contour integral of a complex function II", "functions": {}, "showQuestionGroupNames": false, "parts": [{"scripts": {}, "gaps": [{"showCorrectAnswer": true, "allowFractions": false, "scripts": {}, "type": "numberentry", "maxValue": "u+tol", "minValue": "u-tol", "correctAnswerFraction": false, "marks": 1, "showPrecisionHint": false}, {"showCorrectAnswer": true, "allowFractions": false, "scripts": {}, "type": "numberentry", "maxValue": "v+tol", "minValue": "v-tol", "correctAnswerFraction": false, "marks": 1, "showPrecisionHint": false}], "type": "gapfill", "prompt": "

$I=$[[0]]$+i$[[1]].  (Enter your answers to 3d.p.)

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Find the value of the integral

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\\[I=\\int_C{\\!\\mathrm{e}^{-z}\\,\\mathrm{d}z},\\]

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along any path $C$ from $z=\\var{a1}$ to $z=\\simplify{{b1}+{c1}*i}$.

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15/7/2012:

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Added tags.

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Contour integral of $\\mathrm{e}^{-z}$ along any path.

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This is an exercise in integration, so

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\\[\\begin{align}I&=\\int_C{\\!\\mathrm{e}^{-z}\\,\\mathrm{d}z}\\\\&=\\int_{\\var{a1}}^{\\simplify{{b1}+{c1}*i}}{\\!\\mathrm{e}^{-z}\\,\\mathrm{d}z}\\\\&=-\\left[\\mathrm{e}^{-z}\\right]_{\\var{a1}}^{\\simplify{{b1}+{c1}*i}}\\\\&=\\mathrm{e}^{\\var{-a1}}-\\mathrm{e}^{\\simplify{{-b1}+{-c1}*i}}.\\end{align}\\]

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This can be rewritten as

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\\[I=\\mathrm{e}^{\\var{-a1}}-\\mathrm{e}^{\\var{-b1}}\\biggl(\\cos(\\var{c1})-i\\sin(\\var{c1})\\biggr)=\\simplify{{u}+{v}*i}\\;\\text{to 3d.p.}\\]

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