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In summary, sin(4pi) on a calculator returns -2^-13. Sin(6pi) returns 2E-13, sin(8pi) returns -4E-13, and sin(10pi) returns 1/(2^43).

- #1

1MileCrash

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For sin(4pi), my calculator gives -2^-13.

Obviously, that is really close to the correct value of 0, but it just says 0 for ANY other multiple of pi I've tried.

Weird right?

TI-83 plus.. common calculator. Anyone have issues like this?

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- #2

moouers

- 80

- 0

Ha! Just tried it on my TI-83+ (from 1997), and it shows the same thing. Says the same for Sin4pi. Sin6pi returns 2E-13, and sin8pi returns -4E-13.

My TI-36X Pro, which I use almost exclusively now, returns 0.

- #3

1MileCrash

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Yep, I get those same results as you, never tried those, so my capital ANY was not a very meaningful "ANY," heh.

When it showed this error, I actually decided to graph "sin x" on it, then find the value when x = 4pi.. still returns -2e-13 that way.

Weird.

- #4

jhae2.718

Gold Member

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Welcome to the joys of floating point arithmetic.

- #5

jim hardy

Science Advisor

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Dearly Missed

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hmmmm transcendentals likely calculated by a series...

and 10-13 is about 1/(2^43)

i'm guessing their internal binary arithmetic is good to ~43 bits.

Anybody got an old HP31?

old jim

- #6

Moonbear

Staff Emeritus

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It must be doing the 4*pi calculation first, incorporates some rounding error, then takes the sin of that.

- #7

1MileCrash

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Moonbear said:

It must be doing the 4*pi calculation first, incorporates some rounding error, then takes the sin of that.

But it works fine for something like pi/2 or even 10pi.

- #8

Antiphon

- 1,686

- 4

Try 8 pi.

- #9

SHISHKABOB

- 541

- 1

um, so, I was kind of bored this evening and I saw this thread. Since I love excel and graphs... and numbers, I just started punching multiples of pi into my TI- 83 Plus calculator and noting down the results from 1pi to 100pi.

I got these graphs

the first is the whole shebang, the second is a zoom in on the first portion of the graph

it's interesting I guess, but I don't know enough about calculators to have any idea of why it does it like this. I'm going to keep going, since I have nothing else to do tonight, and see what happens on out from 100pi.

also there is the excel file if anyone feels like looking at the numbers and messing with them

#### Attachments

## Related to Calculator giving weird answers?

## 1. Why is my calculator giving me incorrect answers?

There could be several reasons for this. It could be due to a technical malfunction, incorrect input, or a glitch in the software. Try resetting the calculator or checking your inputs to see if they are correct.

## 2. Can I fix my calculator if it is giving weird answers?

In most cases, yes. Try following the instructions in the user manual to reset the calculator or contact the manufacturer for technical support. If the issue persists, it may be time to replace your calculator.

## 3. Is my calculator broken if it is giving weird answers?

Not necessarily. As mentioned before, there could be various reasons for the incorrect answers. Try troubleshooting the issue before assuming that your calculator is broken.

## 4. Can the battery affect the accuracy of my calculator?

Yes, a low battery can cause your calculator to give incorrect answers. Make sure to replace the battery if it is running low and see if that resolves the issue.

## 5. How can I prevent my calculator from giving weird answers in the future?

To prevent future issues, make sure to follow the instructions for using your calculator properly. Also, keep it away from extreme temperatures, liquids, and other potential sources of damage. Regular maintenance and replacing the battery when needed can also help prolong the life of your calculator.

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