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'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'

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**gAr****Member**- Registered: 2011-01-09
- Posts: 3,479

Hi Agnishom,

You mean as in the one given here: wiki?

Put h = k = m = 1, and you have this equation.

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense" - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,639

Hi;

He can put it in standard form with a rotation of 45 degrees clockwise and a translation by the √2

Just involves the substitutions

of

and then replacing x1 by x1+ √2.

You might download this

http://math.sci.ccny.cuny.edu/document/show/2685

rename the file to Rotation of Axes.pdf This will explain some of this, won't make you as good as scientia or bob bundy with these transformation problems but it is a start.

**In mathematics, you don't understand things. You just get used to them.**

**If it ain't broke, fix it until it is.**

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,067

hi bobbym

Like the light sabre by the way. You beat me to it.

Agnishom: Here's my version:

Substitute* x = X +1 and y = Y + 1, where X and Y are new variables.

So we now have a more familiar XY = 0 (the rectangular hyperbola)

Now substitute* X = x/a - y/b and Y = x/a + y/b

* substitutions like these preserve the hyperbolic nature of the curve.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**scientia****Member**- Registered: 2009-11-13
- Posts: 224

In questions of this sort I tend look for a transformation to get rid of the term:

When this is substituted into the original equation, the term in

isWe want this to vanish, so *any*

Thus under the transformation the curve

becomes the hyperbola . Furthermore as the transformationrepresents a clockwise rotation of 45° about the origin followed by an enlargement of

at the origin, the conic section is preserved, i.e. the original curve is indeed a hyperbola.**NB: Be careful when using linear transformations on curves: only rotations, reflections and enlargements/contractions by a nonzero factor preserve conic sections. Any other transformation may distort the curve and alter its original nature.**

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Ok thanks

'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'

'But our love is like the wind. I can't see it but I can feel it.' -A Walk to remember

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