# trig

This is a discussion on trig within the A Brief History of Cprogramming.com forums, part of the Community Boards category; ahh it was a summation, corrected......

1. ahh it was a summation, corrected...

2. 1 - .9_ = .0_1

If you subtract .9_ from 1, you get a repeating 0 with a 1 at the end, but the one will never happen, even though it is there...so thats how I think you should express it. I also think 1/3 should be expressed like this:

0.3_4

0.3_ never reaches 1/3...it just keeps on approaching it...so wouldnt it be appropriate to have a repeating 3, and then a 4 after the repeating 3 but it just never reaches the 4?

3. Originally posted by DavidP
1 - .9_ = .0_1

If you subtract .9_ from 1, you get a repeating 0 with a 1 at the end, but the one will never happen, even though it is there...so thats how I think you should express it.
No, 1 - 0.9_ = 0. Exactly. If the repeating decimal "never" reaches the one in your notation, why write it? Just call it zero.

I remember inm 10th grade I tried using the same argument against my geometry teacher. 0.9_ isn't one, it's just infinitely close to one, I said. Nothing he could say would convince me otherwise. But actually the reason I was wrong is pretty simple: in mathematics, a value infinitely close to a number is the same as that number.

4. >If the repeating decimal "never" reaches the one in your notation, why write it? Just call it zero.

No...its still not zero. No matter how close it is...its not the same number. And in mathematics, even the slightest errors can be bad.

5. Well, if that doesn't convince you, there's not much I can say. The problem is probably that you don't understand the concept of infinity properly. Perhaps you should take a semester or two of calculus, where the property of convergence of an infinite series to a definite value is used to do all sorts of very useful things, including the justification of the repeating decimal and trigonometric Taylor series.

6. Yet another reason we need the old board back... Need to see the explanations given in "Math Discussion". Then again, maybe we don't

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