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## #1 2010-04-19 05:36:59

FP3Student
Guest

### Intersection of Two Planes

Hello people,

I am a little stuck on this question.

I have two planes with equations r.(3 1 1) = 2 and r.(2 5 -1) = 15 intersect in the line L.

Find a direction for the line L.

How would I do this when I haven't learnt the vector/cross product yet?

Is there another way to do it?

Thank you.

## #2 2010-04-19 09:10:55

Ricky
Moderator
Registered: 2005-12-04
Posts: 3,791

### Re: Intersection of Two Planes

Every line is determined by two distinct points.  Any point that lies in both those planes will be on your line.  So find two distinct points in both those planes, and you'll know everything there is to know about the line.

"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

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