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    Hi guys.

    Can anyone have a look at question 8 part a and help me understand how they have found a point of intersection between the planes, in the first method shown in the mark-scheme.

    I managed to do the question but i converted to cartesian and eliminated variables. And my way looked much longer than the way in the mark-scheme.

    I understand the cross product of the method i just need help with a quick way to find a point of jntersection thanks.

    Question paper-[link]http://pmt.physicsandmathstutor.com/...%20Edexcel.pdf[/link]

    Markscheme-[link]http://pmt.physicsandmathstutor.com/...%20Edexcel.pdf[/link]

    Thanks
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    You're given the equation of two planes, substitute some value (an easy one like x=0)
    then solve the equations simultaneously to find a point of intersection. Remember to replace r by a general vector (x,y,z) and then work out the dot product. This will be a position on the line of intersection.

    The vector normal to the 2 normals is parallel to the line of intersection. This is the direction vector.

    So then its just position + direction.
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    (Original post by NotNotBatman)
    You're given the equation of two planes, substitute some value (an easy one like x=0)
    then solve the equations simultaneously to find a point of intersection. Remember to replace r by a general vector (x,y,z) and then work out the dot product. This will be a position on the line of intersection.

    The vector normal to the 2 normals is parallel to the line of intersection. This is the direction vector.

    So then its just position + direction.
    Legend.

    Now that you’ve said it I’m kicking myself that i didn’t realise i sooner.

    Definitely much quicker than the method i used.

    Thanks a bunch.
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    (Original post by Shaanv)
    Legend.

    Now that you’ve said it I’m kicking myself that i didn’t realise i sooner.

    Definitely much quicker than the method i used.

    Thanks a bunch.
    No problem
 
 
 
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