// Numbas version: exam_results_page_options {"name": "Harry's copy of Graph solution", "extensions": ["jsxgraph"], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"tags": [], "functions": {}, "statement": "

Drag the points on the graph to sketch the formula y = \$x^2 + 4x + 2\$

", "name": "Harry's copy of Graph solution", "advice": "", "variables": {"c": {"definition": "random(-4..4 except 0)", "description": "", "group": "Ungrouped variables", "name": "c", "templateType": "anything"}, "a": {"definition": "random(-2,-1,-0.5,0.5,1,2)", "description": "", "group": "Ungrouped variables", "name": "a", "templateType": "anything"}}, "ungrouped_variables": ["a", "c"], "extensions": ["jsxgraph"], "variable_groups": [], "metadata": {"description": "

Drag points on a JSXgraph plot to sketch solution

", "licence": "Creative Commons Attribution 4.0 International"}, "rulesets": {"std": ["all", "fractionNumbers"]}, "preamble": {"js": "function dragpoint_board() {\n var scope = question.scope;\n \n var a = scope.variables.a.value;\n var c = scope.variables.c.value;\n var maxy = Math.max(Math.abs(a*9+c),Math.abs(c));\n \n var div = Numbas.extensions.jsxgraph.makeBoard('250px','400px',{boundingBox:[-5,maxy+3,5,-maxy-3],grid:true});\n question.display.html.find('#dragpoint').append(div);\n \n var board = div.board;\n \n //shorthand to evaluate a mathematical expression to a number\n function evaluate(expression) {\n try {\n var val = Numbas.jme.evaluate(expression,question.scope);\n return Numbas.jme.unwrapValue(val);\n }\n catch(e) {\n // if there's an error, return no number\n return NaN;\n }\n }\n \n // set up points array\n var num_points = 7;\n var points = [];\n \n \n // this function sets up the i^th point\n function make_point(i) {\n \n // calculate initial coordinates\n var x = i-(num_points-1)/2;\n \n // create an invisible vertical line for the point to slide along\n var line = board.create('line',[[x,0],[x,1]],{visible: false});\n \n // create the point\n var point = points[i] = board.create(\n 'glider',\n [i-(num_points-1)/2,0,line],\n {\n name:'',\n size:2,\n snapSizeY: 0.1, // the point will snap to y-coordinates which are multiples of 0.1\n snapToGrid: true\n }\n );\n \n // the contents of the input box for this point\n var studentAnswer = question.parts[1].gaps[i].display.studentAnswer;\n \n // watch the student's input and reposition the point when it changes. \n ko.computed(function() {\n y = evaluate(studentAnswer());\n if(!(isNaN(y)) && board.mode!=board.BOARD_MODE_DRAG) {\n point.moveTo([x,y],100);\n }\n });\n \n // when the student drags the point, update the gapfill input\n point.on('drag',function(){\n var y = Numbas.math.niceNumber(point.Y());\n studentAnswer(y);\n });\n \n }\n \n // create each point\n for(var i=0;iThe graph of this formula is:

", "shuffleChoices": false, "choices": ["

An upwards-opening parabola

", "

A downwards-opening parabola

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