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# Line of intersection of two planes watch

1. Hi guys can anyone have a look at question 8 part c.

I went with way 2 however way 1 on mark scheme seems a lot simpler so i was hoping someone could explain why they did what they did. If i were to replicate this method for another similar question would i always get a correct answer or is there something unique about this question.

Thanks

Edit: so by working backwards ive deduced that the normal to both of the planes normals gives the direction of the line of intersection.

This is because the normal to the normal to both planes must be perpendicular to both the two planes.

Is this correct?
2. (Original post by Shaanv)
Edit: so by working backwards ive deduced that the normal to both of the planes normals gives the direction of the line of intersection.

This is because the normal to the normal to both planes must be perpendicular to both the two planes.

Is this correct?

Its simply because the the normal to the two normals must be a vector parallel to both planes. This is precisely the line of intersection. All that’s needed after is just getting a single point the line must pass through, ie a single point on both planes.
3. (Original post by RDKGames)

Its simply because the the normal to the two normals must be a vector parallel to both planes. This is precisely the line of intersection. All that’s needed after is just getting a single point the line must pass through, ie a single point on both planes.
Thanks a bunch.I was trying to say what u said.

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Updated: February 24, 2018
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