我在做圆的时候出现拉一点问题 求大家帮我解答 着急

Question

function bb(){

 var canvas = document.getElementById("canvas");

 canvas.width = 260;

 canvas.height = 260;

 var context = canvas.getContext("2d");

 

 context.beginPath()

 context.lineWidth = 30

 context.strokeStyle = "orange"

 context.arc(130, 130,100,0,0.5*Math.PI)

 context.stroke()

 context.closePath()

 

context.beginPath()

 context.lineWidth = 30

 context.strokeStyle = "red"

 context.arc(130, 130,100,0.5,1*Math.PI,false)

 context.stroke()

 context.closePath()

  

为什么我的第二段路径不从0.5PI起到1PI