//画正弦曲线 //dot 原点 //amplitude    振幅 -- A //initialPhase 初相 -- φ //setover 偏距 -- k //palstance 角速度 -- ω //len 周期数 function drawSinusoid(dot, amplitude,initialPhase,palstance,setover, len, opts){     var color = opts&&opts.color?opts.color:"DarkRed"; //曲线的颜色     var max = len*2*Math.PI/w; //x的最大值     //var x = -2*Math.PI/w/3;     var x = 0; //x的初值     var pre = [dot[0]+x, dot[1]+(amplitude*Math.sin(palstance*x+initialPhase)+setover)]; //y的初值     for(;x < max;x+=5){ //每五个单位画一条线         var cur = [dot[0]+x, dot[1]+(amplitude*Math.sin(palstance*x+initialPhase)+setover)];         drawLine(pre, cur, {color: color}); // 画线         pre = cur;     }     var d = Math.PI/(2*w);     for(var x =0;x < max;x+=d){//描点         var cur = [dot[0]+x, dot[1]+(amplitude*Math.sin(palstance*x+initialPhase)+setover)];         drawPoint({             pw:3,ph:3,color:'DarkRed',point: cur         });     }         var pend = [dot[0]+max, dot[1]+(amplitude*Math.sin(palstance*max+initialPhase)+setover)];     drawPoint({         pw:3,ph:3,color:'DarkRed',point: pend     });     drawLine(pre, pend); }