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You are not logged in. #2 20130811 22:39:01
Re: Parabola anglePost in help me section 'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.' 'God exists because Mathematics is consistent, and the devil exists because we cannot prove it' 'Who are you to judge everything?' Alokananda #3 20130812 05:16:53
Re: Parabola anglehi umunna You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #4 20130812 19:09:28
Re: Parabola angleHello Bob, thanks for your explanations , I have presently a 4 meter in diameter with the following statistics , dept 65cm , and focal point of 152cm. #5 20130812 20:45:49
Re: Parabola angleOK, thanks for the additional data. I'm in the middle of some woodwork at the moment and only stopped for a coffee. I'll work out a formula later today. (My time 11.45 now) You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #7 20130812 22:22:29
Re: Parabola angleSome info at bottom of this page also: Parabola "The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  Leon M. Lederman #8 20130812 22:44:16
Re: Parabola angleThanks MIF. So far I've just worked in two dimensions. The parabolic reflector for a dish is made by rotating the curve around the x axis in a circle. For your measurements (make sure you convert cm to m) a = 1.52 My second diagram shows a point with y coordinate 2. This is because you gave the diameter as 4m so the radius will be 2. calculating: which I make 0.65789. So I've rounded up to 0.658. For your new dish you will have y = 2.35. You can choose an x and hence find a or the other way round. Good luck with the build. Bob You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #10 20130814 03:32:42
Re: Parabola angleOK. The centre of the dish is at (0,0). The x axis runs out towards the focus. The y axis is at right angles to this. where the focus is at (a,0) You want a diameter of 4.7 m That means the radius (distance from the x axis) is 2.35 m And you want a = 1.8 m So the depth of the dish will be To make a card former for points on the surface of the dish, you need to plot the graph If you compute y for a set of values of x using this: you will get the top half of the curve. You could calculate coordinates using a calculator and plot the graph, or maybe, use a graph plotter. There are plenty available on the net. Good luck ... let me know how it goes. Bob You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #12 20130822 04:19:38
Re: Parabola anglehi umunna You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei 