studiot

I don't know when masons started carving dates into their work, possibly in Roman times. But it was certainly well known practice by the middle ages.

Meaning what?

Was that a reply to my question? How about something like The flow under gravity of golden syrup round polished steel balls showing drag coefficients for a range of Reynolds numbers, at 50degC.

Yes it's your arithmetic. Tell me, why did you not write the equation in the order that you presented the information in your post#1? I did ask which was the largest. The square of the largest (C2) equals the sum of the squares of the other two (A2 +B2) minus 45 C2 = (A2 +B2) - 45 Substitute from my 3 equations for x (x+2)2 = x2 + (x+1)2 - 45 expand and collect terms x2 - 2x -48 = 0 note in these forums the superscript and subscript icons on the toolbar at the top of the edit window

I looked, but could not find any reference to what your graph referred to as it had no title or explanatory key. Oh and thank you for your response to my post#11.

OK, here's the griff. The variable x is what is called a 'parameter'. The idea of a parameter is that we put everything in terms of that parameter. That is we write equations connecting the parameter to the unknowns. Since there is then one equation in only one unknown (the parameter) it can be solved. You will find that parameters are used in many situations in maths to simplify and connect apparently unconnected quantities. In your specific question there are three unknowns. Let as call them A, B and C So A = x B = (x+1) C = (x+2) Which is the largest? Can you now write an equation connecting A, B and C (but not containing x) from the information given. Post your equation or explain your difficulty Can you see the next step?

Hmm non even expressions of pi in formulae in simple math off the top of my head? [math]E = a + b + c - \pi [/math] [math]V = \frac{4}{3}\pi {r^3}[/math] [math]A = \pi {r^2}[/math] [math]\cos x = \sin \left( {x + \frac{\pi }{2}} \right)[/math] [math]y(x,0) = f(x) = \frac{{8A}}{{{\pi ^2}}}\left( {\frac{1}{{{1^2}}}\sin \frac{{\pi x}}{l} - \frac{1}{{{3^2}}}\sin \frac{{3\pi x}}{l} + \frac{1}{{{5^2}}}\sin \frac{{5\pi x}}{l} - \frac{1}{{{7^2}}}\sin \frac{{7\pi x}}{l} + ..........} \right)[/math] And who are you to tell me that I have to use the radius? However, just to humour you, I have used the radius in the above, where appropriate.

Yes isn't it? Changing to tau would certainly work since both pi and tau are only numbers. Such a change would undoubtedly benefit some uses. Equally certainly it would make some applications harder. You have utterly failed to demonstrate that any net benefit would accrue from such a change. or even that the situation would not deteriorate. Surely a properly researched and reasoned proposal would examine both sides dispassionately and weigh these in the balance, rather than predetermining the issue by only demonstrating the supporting evidence. That would be proper Science. The other is the Method of Politicians.

Are you trying to replace the perfectly servicable number 1 with tau?

Since you have highlighted my caveat, you presumably read it. A non integer ratio or any other number makes less sense than unity as the basis for counting turns.

If all you really want is to denote turns (circles), then why 2pi? Why not much more simply 1 turn, 2 turns 3.378 turns...............? But wait, engineers already do that , and have a symbol for it - usually n or N. So what rpm does the dial on your dash show? Or what is the transformer turns ratio ? And then, of course, you could decimalise it. But wait again, europeans already do that, they call them grads.

I'm sorry I don't follow what this is referring to.

So there is no gain in doubling pi, you still have the factor of 2 around. What about all the electrodynamic equations that contain some multiple of pi somewhere?

Circles are only two dimensional. We live in a three dimensional world. There may be 2pi radians in a two dimensional circle but how many steradians are there in a sphere?

The first ten minutes of this Walter Lewin lecture are a masterpiece of all that has been discussed here. Maths is used in Physics, ie physical laws and principle are stated mathematically. But Physics knowledge is used to determine, alter and tailor the maths to suit the situation. So Physics leads Maths to a useful analysis. But maths strikes back as an ajb type analysis of errors. All is in proper balance. http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/lecture-17/

Bullets are tested in apparatus known as a ballistic pendulum. You might like to watch this video. http://www.youtube.com/watch?v=l87Dr2lJEOk

Drawbacks? How much do you think it cost to create the existing power grid? £ Billions?,£ Trillions? If all this was torn down and replaced with another system that also cost £billions? £trillions? Who would pay? Why the consumer of course. Do you have any idea how much higher our bills would have to be to make such a change?

This discussion seems to be going round in circles. Can I suggest that the difference between analysis and synthesis be given an airing? It is very easy to measure and describe something existing and observable by means of mathematics. It is not so easy to create something to order and mathematics is often silent on the way to achieve this, although it may help confirm when you arrive. Not all science and technology is amenable to the language of mathematics. Take, for example, the flat plates I mentioned earlier. Mathematical analysis of measurements can tell you when the plates are flat, but it has nothing to offer on ways to achieve flatness.

What you have to remember is that the coefficient of friction refers to both contacting surfaces. So any statement of the type " The coefficient of friction of steel, rubber, carbon coating...is x" is basically meaningless. You need to state "carbon on carbon", "steel on ice" or whatever.

The Mechanics of Flight A C Kermonde, Fellow of the Royal Aeronautical Society Pitman Volume1 should fit the bill nicely.

If I am reading your intentions correctly neither diagram is correct. 1) In both diagrams the electric force should be the same number at all points in that diagram. 2) In both diagrams the energy to the right should equal the energy to the left. The energy is determined by the number used in my point#1

If you divide the general equation through by one of the constants you can reduce the number of points to 5, that is you can fit a conic to any 5 points. I am not sure about three intersecting conics but two overlaid conics will intersect at four points. These points may be real or imaginary depending upon conic type and orientation. Ed Earl A parabola results if the intersecting plane is parallel to any line passing through both the base and the vertex of the cone, ie parallel to the side of the cone. Does this help or do you need more, What exactly are you looking for? Really this thread is about the two dimensional co-ordinate geometry of conics, not their generation by intersecting three D objects. So if you want more you should really start your own thread. You will note that the general formula above only refers to two axes (x and y).

Is your interest in doubling the value of the constant (pi is transcendental, not irrational) aestetic, perhaps because there are 2pi radians in a circle?

Unfortunately far to many medical staff believe their calculators, rather than my wife who tries to teach them to understand. The result is a sometimes fatal drug error. Thank you for your comment on my simple example. Yes there is a grey area (as always) and it can be difficult to know at what point to decide "this is not maths". Here is a simpler example, again from the domain of surveyors. In days of yore surveyors used to measure distance by laying out a physical chain. Surveyors were advised to count the number of layings of the chain by picking up a small stone and placing it in a pocket each time or by transferring a stone each time from a collection. An what about tally sticks used by primitives, who cannot actually count up to their tally?

So what do you use pi for? As a matter of interest is 2pi an even number and is pi even or odd?