So I wanted to make a trig solver in javascript?

Question

But when I ran the Math.cos(1) It was different than the cos my calculator returned, would that make a difference with the answer? Will it return a different value?

On my calculator I tested 4 x cos(3) and in js I tested 4 * Math.cos(3).

They were both different, in js these were the first few numbers -3.9599 and on my calc 3.9945

Are you using the right units? (degrees or radians) - that would be the first thing to check... — John3136, Aug 13 '13 at 06:49
Why would you post a question like this and NOT supply the two different answers that you got? — DevlshOne, Aug 13 '13 at 06:50
On my calculator I tested `4 x cos(3)` and in js I tested `4 * Math.cos(3)` — Samir, Aug 13 '13 at 06:50
They were both different, in js these were the first few numbers `-3.9599` and on my calc `3.9945` — Samir, Aug 13 '13 at 06:52

score 2 · Answer 1 · answered Aug 13 '13 at 06:53

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Math.cos() expects it's argument in radians. Your calculator is set for degrees.

cos(3) radians = -0.9899

cos(3) degrees = 0.9986

answered Aug 13 '13 at 06:53

John3136

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score 2 · Answer 2 · edited May 23 '17 at 12:20

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Math.cos(x), where x is A number given in unit of radians.

I'm assuming you're expecting 0.999(...) [degrees] but are seeing 0.540(...) [radians] coming from JavaScript.

But, you're in luck! There is a questions on SO regarding how to convert to degrees.

edited May 23 '17 at 12:20

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answered Aug 13 '13 at 06:54

Brad Christie

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what about the `sin-1` is there a function for that? – Samir Aug 13 '13 at 07:12
[`Math.asin`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/asin)? (arcsin is what you're looking for) – Brad Christie Aug 13 '13 at 07:15

score 0 · Answer 3 · edited May 23 '17 at 11:49

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can you post the 2 values that you got? I blindly think you're dealing with http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems . And if this is the issue, I think you will have to check if the results are within a certain tolerance, as Alnitak said here: How can i make the php cos function return the correct value?

edited May 23 '17 at 11:49

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answered Aug 13 '13 at 06:53

Nicolae Olariu

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So I wanted to make a trig solver in javascript?

3 Answers3