//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);}