CODEWITHSUNDEEP
javascriptmath
Yamaha32088
Yamaha32088

Reputation: 4163

Understanding function

I am having trouble understanding a function hopefully someone can help me out here. I am trying to find the pitch diameter of a sprocket the function for this in JavaScript is:

function sprocket_diam(dataform,pitch,teeth)
{



   var a,b,c,d,e;

   a = pitch / 2;
   b = teeth * 2;
   c = 360 / b;
   d =  Math.sin ((c * Math.PI) / 180);
   e = (a / d) * 2



    dataform.diam.value = e;

}

The above function works just as intended but I am trying to do this by hand on a calculator. I think the problem I am having comes in the d variable. For example lets say I have a 15 tooth sprocket with a pitch of .5". Using the above formula the numbers for the variables I get are: a=0.25,b=30,c=12, and for d I take (12*3.14)/180 which gives me 0.2093 so e=(0.25/.2093)*2 which ends up being 2.388915432 but is the incorrect answer it should be 2.404867172372066 Can someone point out what I am doing wrong? I have always struggled with math.

Upvotes: 0

Views: 87

Answers (2)

Rok Burgar
Rok Burgar

Reputation: 949

You didn't compute the sinus. (Math.sin)

Upvotes: 3

Denys Séguret
Denys Séguret

Reputation: 382160

Your error is that you do as if Math.PI would be 3.14.

If you use the precise value of Math.PI, you get 12*Math.PI/180 == 0.20943951023931953 instead of the 0.2093 you use and at the end you find 2.404867172372066

Upvotes: 1

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