# How do you find the zeroes of a discrete function?

1. Jun 20, 2012

### Frogeyedpeas

Would Newton's method or some other method work? Consider the following problem:

find the zeroes of the function: y = 40sin(2x) - floor(40sin(2x))

where Y,X $\in$ R

I don't exactly know how to handle this problem. My best insight so far is that it is only equal to zero whenever 40sin(2x) is an integer. But even then the distribution of these integers is quite random and I honestly don't know any inverse-floor function.

2. Jun 20, 2012

### algebrat

Could you tell us a little more about what class this is from, and what kind of similar problems you may have encountered, and tell us a little about the techniques you're class us covering?

3. Jun 20, 2012

### Frogeyedpeas

ehhh not exactly from a class (sorry), and I don't have any sample problems for this thing either. It just kind of came up. My best guess is to use Newton's formula.

I mean Newton's method

Last edited: Jun 20, 2012
4. Jun 20, 2012

### Frogeyedpeas

So this problem i basically the same thing as frac{40sin(2x)} = 0.

5. Jun 20, 2012

### Frogeyedpeas

w8 nvm i'm good, I got the method

6. Jun 20, 2012

### algebrat

So what was the method? Where did the problem come up?

7. Jun 20, 2012

### Frogeyedpeas

Well it turns out if you do an iterated newton method the number works. To speed things up i broke up the function into seperate segments defined as linear. The function appeared out of the context of being given a discrete function how do you make a contonuous analog