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the intersection of two planes

the intersection of two planes

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g
Wayward Soul

Your Blackened Sky

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today in maths we were tought how to find the equation of the line on which two planes intersect. the actualy doing it isn't to hard...but one bit confuses me...

the first thing you do is find a point on this line. to do this, we were tought to set Z on the planes to 0, then you can find the other points of intersection (X and Y) with symultaneous equations. but if Z doesn't work, try Y, and if Y doesn't, try X. and if it doesn't, they're parrallel...

but why? what if the planes were smaller and didnt cross any of the axises?!?

i'm confuddled...

but yeah-second part of the prelim tomorrow...i gotta go revise...😵

T

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'cos to be a plane, they have to be infinite.

g
Wayward Soul

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Originally posted by Toe
'cos to be a plane, they have to be infinite.
oooh-that makes sense...but isn't a plane defined by two lines?

*confused*

again...

r

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An easy way to find the line of intersection between two planes is to set both equations equal to each other and solve. You will end up with either of the following:

1) The equation of a line, which implies that the planes do intersect and are not coincidental.
2) The equation of a plane, which implies that the two planes were coincidental.
3) A contradiction, which implies that the planes are parallel.

-Ray.

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