# Dapthar

Senior Members

169

• Baryon

## Profile Information

• College Major/Degree
Mathematics, Electrical Engineering
• Favorite Area of Science
Mathematics
• Biography
Student

10

1. ## hey there any free engineering reference site?

What kind of engineering reference are you looking for? Chemical, Electrical, Mechanical, Nuclear, or something else? If you could be a tad bit more specific, it would help.
2. ## Is Noise Cancelling Done Biologically?

I've been wondering about the benefits of noise cancelling headphones. For those who aren't familiar with these devices, they essentially generate a sound wave that is $180^o$ out of phase with the low-frequency noise that is picked up by the microphones that are present in the headset. For example, see the attached picture. If the noise waveform was the red sine wave, the waveform generated by the headphones would be the blue sine wave, and when added together, these waveforms cancel out, resulting in no sound. (Note this is an idealized view, in reality the headphones can't generate the "anti-noise" waveform immediately, resulting in an incomplete cancellation, which is perceived as a quiet hissing sound.) However, my question is, is this addition of waveforms done in the air, or by one's ear? The reason I ask is if the cancellation is done in the air, then no sound actually reaches one's ear, and thus the ear does no work. But, if and the summation is done inside one's ear, i.e. biologically, then the ear is working twice as hard as it has to, leading to the twice the damage that constant exposure to the noise would inflict.
3. ## In what order should I go through Math subjects?

The number of Calculus classes usually varies by institution. A typical division is: Calculus I: Covers limits, continuity, symbolic and numerical derivatives, and applications of these topics. (Restricted to one dimension) Calculus II: Covers symbolic and numerical integration, advanced integration techniques, Taylor series, and applications of these topics. (Again, restricted to one dimension) Calculus III: Extension of differentiation and integration to n dimensions (with most of the time being spent on functions of two independent variables), vector calculus, and applications of these topics. The above topics are sometimes shifted between classes, but usually maintain the same relative order, e.g., basic symbolic and numerical integration may be shifted to Calculus I, but differentiation is in all but the rarest cases, taught before integration. Also note that the above structure is closely follows that of the text I learned Calculus from, authored by Edwards and Penney.
4. ## Finding Square Roots Manually

It depends on what you mean by "best". If you want a simple' date=' and quick way to get a reasonably accurate estimate of a square root, try the first method on this page: http://mathforum.org/dr.math/faq/faq.sqrt.by.hand.html If you want a more accurate approach, you could use the Binomial Theorem, and the details of how to use such a method are also on the aforementioned page, under the heading [b']Square Roots Using Infinite Series[/b].
5. ## Ender's Game

I suggest reading the "2001" series by Arthur C. Clarke. Namely: 2001: A Space Odyssey 2010: Odyssey Two 2061: Odyssey Three 3001: The Final Odyssey In general, anything Clarke has written by himself is worth reading, while books he co-authors tend to be lackluster.

7. ## Apple to Announce Intel Conversion Monday

I wonder how this will play with Intel's decision to begin embedding Digital Rights Management hardware into their dual core processors. But then again, Apple seems to have dealt with the DRM/iPod issue in a manner that hasn't alienated their user base.

9. ## New Server

Could you please make the SFN logo at the top left of the page link to the SFN homepage once again? Apparently the link was broken/forgotten when the style was updated. Thanks.
10. ## Higher-level language

There's Java. Not much else immediately springs to my mind besides C#, but that's a variant of C++.

12. ## A Geometric progression problem.

It looks right to me. I would have worked out this problem in the same manner, since it seems to call for an algebraic approach.
13. ## Real number axioms

I don't really have a personal version per say, I'm just quoting from memory. If you'd like, I can dig up my old Abstract Algebra book and post those field axioms here. Alternatively, I can just tell you the page number if you already have access to his book; Algebra by Michael Artin.
14. ## Real number axioms

I believe associativity and commutativity are all that's left.
15. ## Real number axioms

Yup. My mistake. I've fixed the original post.
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