[从头学数学] 第142节 平行四边形

剧情提要：
[机器小伟]在[工程师阿伟]的陪同下进入了筑基中期的修炼，
这次要修炼的目标是[平行四边形]。

正剧开始：

星历2016年03月20日 09:42:00, 银河系厄尔斯星球中华帝国江南行省。
[工程师阿伟]正在和[机器小伟]一起研究[平行四边形]。

<span style="font-size:18px;">		var r = 20;
		config.setSector(1,1,1,1);  
		config.graphPaper2D(0, 0, r);
		config.axis2D(0, 0,180);  
	
		var triangle = new  Triangle();  
		var a = [];
		var tmp = [];
		
		config.setSector(3,3,1,1);  
		a = shape.paraquad(0, 0, 0, 10, 5, Math.PI/6);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'red', 20);
		
		config.setSector(3,3,2,1);  
		a = shape.paraquad(0, 0, 0, 5, 10, Math.PI/6);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'green', 20);</span>

<span style="font-size:18px;">	this.paraquad = function(x, y, rot, a, b, angle) {
		angle = angle ? Math.abs(angle) : 0;
		rot = rot ? rot : 0;
		//参数说明：
		//平行四边形的两条边a, b, 以及它们之间的夹角angle
		//这个平行四边形的起始点(x, y), 以及整个图形与x轴的夹角rot
			
		var retArray = new Array();
		retArray.push([x, -y]);
		retArray.push([x + a * Math.cos(rot), -(y + a * Math.sin(rot))]);
		retArray.push([x + a * Math.cos(rot)+ b * Math.cos(rot+angle), 
					  -(y + a * Math.sin(rot)+ b * Math.sin(rot+angle))]);
		retArray.push([x + b * Math.cos(rot+angle), -(y + b * Math.sin(rot+angle))]);
		
		return retArray;
	}</span>

<span style="font-size:18px;">		var r = 20;
		config.setSector(1,1,1,1);  
		config.graphPaper2D(0, 0, r);
		config.axis2D(0, 0,180);  
	
		var triangle = new  Triangle();  
		var a = [];
		var tmp = [];
		
		config.setSector(3,3,1,1);  
		a = triangle.know2edges([10, 8], -90);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'red', 20);
		
		
		config.setSector(3,3,2,1);  
		a = shape.paraquad(0, 0, 0, 6, 10, 53.13/180*Math.PI);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'green', 20, 'BCDA');</span>

<span style="font-size:18px;">		var r = 20;
		config.setSector(1,1,1,1);  
		config.graphPaper2D(0, 0, r);
		config.axis2D(0, 0,180);  
	
		var triangle = new  Triangle();  
		var a = [];
		var tmp = [];
		/*
		config.setSector(3,3,1,1);  
		a = triangle.know2edges([10, 8], -90);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'red', 20);
		*/
		
		config.setSector(3,3,2,1);  
		a = shape.paraquad(0, 0, 0, 10, 10, 60/180*Math.PI);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'green', 20);
		
		a = triangle.know2edges([10, 10], 120);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'red', 20, 'ABE');
		
		a = triangle.know2edges([10, 10], 60);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'pink', 20);
</span>

<span style="font-size:18px;">		var r = 20;
		config.setSector(1,1,1,1);  
		config.graphPaper2D(0, 0, r);
		config.axis2D(0, 0,180);  
	
		var triangle = new  Triangle();  
		var a = [];
		var tmp = [];
		/*
		config.setSector(3,3,1,1);  
		a = triangle.know2edges([10, 8], -90);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'red', 20);
		*/
		
		config.setSector(3,3,1,2);  
		a = shape.paraquad(0, 0, 0, 10, 10, 90/180*Math.PI);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'green', 20);
		
		a = shape.paraquad(-5*0.5, 5*0.707, Math.PI/6, 10, 10, 90/180*Math.PI);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'red', 20, 'EFGH');</span>

<span style="font-size:18px;">		config.setSector(3,3,1,1);  
		a = shape.paraquad(0, 0, 0, 10, 6.18, 90/180*Math.PI);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'red', 20);
		
		a = [[0, -3.09], [10, -3.09]];
		tmp = [].concat(a);
		shape.multiLineDraw(tmp, 'green', 20);</span>

<span style="font-size:18px;">		config.setSector(3,3,1,1);  

		
		a = triangle.know2edges([1, 2]);
		tmp = [].concat(a);
		shape.angleDraw(tmp, 'green', 80);
		
		
		config.setSector(3,3,1,2);  
		a = shape.paraquad(0, 0, 0, 2.24, 2.24, 63.23/180*Math.PI);
		
		tmp = [].concat(a);
		//document.write(tmp);
		shape.angleDraw(tmp, 'red', 80);</span>

本节到此结束，欲知后事如何，请看下回分解。