## Profile

Martin Moene
Works at Universiteit Leiden
Attended HTS Amsterdam
75 have him in circles

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### Martin Moene

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ACCU C Vu 26-1: March's C Vu Journal has been published.

http://accu.org/journal (members only)

#programming #linq #cpp14 #archaeology #raspberrypi  ﻿
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### Martin Moene

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Interesting fact - as you can remember the value of the sine and cosine of the angle 0◦, 30◦, 45◦, 60◦, 90◦.﻿
The fingers are numbered sequentially numbers : {0, 1, 2, 3, 4}.
Trigonometric sine (blue) function is calculated from the bottom.
Trigonometric cosine (red) function is calculated in advance.
Always insert the numbers into the formula √N/2 where N={0, 1, 2, 3, 4}.
We obtain:
sin 90◦ = cos 0◦ = 1
sin 60◦ = cos 30◦ = √3/2
sin 45◦ = cos 45◦ = √2/2
sin 30◦ =  cos 60◦ = ½
sin 0◦ = cos 90◦ = 0﻿
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### Martin Moene

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so...  what about the YouTube Like button - is it real?  (oh - I just clicked it)﻿
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### Martin Moene

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Video of a tricycle made with square wheels that rolls:'
Square-Wheeled Tricycle

So the question is, what is the shape of those 'bumps' which allow a square-wheeled bike or wheels of other regular polygons to ride smoothly? (I didn't know.) Not circles, not parabolas, not cycloids. They are inverted cataneries, the shape a chain makes when hanging freely. What an interesting property of the catenary that you can ride a square-wheeled bike on it! The Arch in St. Louis is also an inverted catenary as well. The formula for a catenary involves cosh, the hyperbolic cosine function. From Wolfram Mathworld:

The curve a hanging flexible wire or chain assumes when supported at its ends and acted upon by a uniform gravitational force. The word catenary is derived from the Latin word for "chain." In 1669, Jungius disproved Galileo's claim that the curve of a chain hanging under gravity would be a parabola. The curve is also called the alysoid and chainette. The equation was obtained by Leibniz, Huygens, and Johann Bernoulli in 1691 in response to a challenge by Jakob Bernoulli.

Huygens was the first to use the term catenary in a letter to Leibniz in 1690, and David Gregory wrote a treatise on the catenary in 1690. If you roll a parabola along a straight line, its focus traces out a catenary. As proved by Euler in 1744, the catenary is also the curve which, when rotated, gives the surface of minimum surface area (the catenoid) for the given bounding circle.

#math   #mathematics   #geekhumor   #scienceeveryday  ﻿
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### Martin Moene

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#programming #cplusplus #catch #testing #java #bignumber  ﻿
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### Martin Moene

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Nice post about unique_ptr, scoped_ptr and (mis)use of shared_ptr.
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### Martin Moene

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"I would submit that the appearance of hard work is often an indication of failure. Software development often isn't done well in a pressurised, interrupt driven, environment."﻿
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### Martin Moene

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Static polymorphic named parameters in C++
This article first appeared in ACCU's Overload Journal issue 119 of February 2014. For a new kind of measurement in our application for scanning probe microscopy [Wikipedia-a], I need to construct a curve that consists of several kinds of segments. The curv...﻿
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In his circles
132 people
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Education
• HTS Amsterdam
Elektrotechniek - Communicatie techniek, 1977 - 1981
• Scholengemeenschap Pascal, Amsterdam
Gymnasium β, 1971 - 1977
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