Month: December 2016

Technology: how a metal detector works

The tutor gives a nontechnical explanation of how a metal detector functions. Watching Curse of Oak Island on the History channel, you see them use metal detectors. How does a metal detector work? A basic explanation is this: The search

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JavaScript: literal string with the concat() function

The tutor shares an observation about the concat() function. The concat() function is used to join one or more strings to the end of another: var strng0 = “This string, “; var strng1 = “then this one” var strng2 =

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Statistics: linear regression on the HP-10B

The tutor shows how to get a best-fit line with the HP-10B. Imagine the following data: x y 3 10.1 4 14.7 9 32.5 12 47.1 To get a best-fit line for it of form y=mx+b, here are the steps:

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Turkey: dark vs white meat

The tutor compares the fat content of white and dark turkey meat. Apparently, cooked turkey thigh (dark meat) is about 5.9% fat, whereas cooked turkey breast (white meat) is about 1.2% fat. Lean roast beef, by comparison, is about 6.4%

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Home computer use: Windows 7: task manager, audiodg.exe, and AudioSrv

The tutor shares some experience about investigating a computer that is running fast. When no-one is using a computer, and it’s not meant to be doing anything in particular, it might be expected to be idle. Sometimes, however, the Windows

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Calculus: derivative of an inverse: derivative of arcsin

The tutor shows the derivative of arcsin, the inverse of sin. In yesterday’s post I explained the formula for the derivative of an inverse function (m-1(x))’ = 1/m'(m-1(x)) Today, I’ll use it to find the derivative of “inverse sin(x)”, aka

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Calculus: the derivative of an inverse function

The tutor shows the development of a formula for the derivative of an inverse. Let’s imagine m(x) is a function with inverse m-1(x). Then m(m-1(x)) = x By implicit differentiation, [m(m-1(x))]’ = 1 By the chain rule, [m(m-1(x))]’ = m'(m-1(x))*(m-1(x))’

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Calculus: an arctan integral

The tutor shows the example ∫dx/(x2+6) ∫dx/(x2+1) = arctanx + C The related integral ∫dx/(x2+6) must be put in the form, as follows: ∫dx/(x2+6) = ∫dx/(6(x2/6+1)) = 1/6 ∫dx/(x2/6 + 1) =1/6 ∫dx/((x/√6)2+1) = (√6)/6∫(dx(1/√6))/((x/√6)2 + 1) Next it becomes

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Math: evaluating transcendental functions: Taylor polynomial for square root

The tutor looks at forming a Taylor polynomial with the example of square root 31. A transcendental function is one there is no operation for. Rather, it’s represented by a series of expressions. Square root and sin are two examples.

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Statistics: Spreadsheets: the frequency() function

The tutor shares a nice function that seems to work the same in Excel or LibreOffice Calc. The frequency() function tells, from an array of values and another of categories, the frequency in each category. A potential use is to