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Quick FP1 matrices question guys!! What's going on?!!!! Watch

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    (Original post by SamePrice)
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    So how do you find the SF of an enlargement from a matrix?
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    (Original post by Muttley79)
    So how do you find the SF of an enlargement from a matrix?
    Well I know the area scale factor is the determinant, but as for the enlargement sf i was under the impression that it was the number which replaces the 1's in the identity matrix, in this case root 3 but that's not the answer
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    (Original post by SamePrice)
    Well I know the area scale factor is the determinant, but as for the enlargement sf i was under the impression that it was the number which replaces the 1's in the identity matrix, in this case root 3 but that's not the answer
    Is the answer 2?
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    (Original post by Muttley79)
    Is the answer 2?
    Indeed it is! I tried to decipher the mark scheme but I honestly haven't been taught whatever it's trying to do.

    Which method did you use?
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    (Original post by SamePrice)
    Indeed it is! I tried to decipher the mark scheme but I honestly haven't been taught whatever it's trying to do.

    Which method did you use?
    Well, as you said, the deteminant gives you the area SF. So how do we get a length scale factor from that?
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    (Original post by Muttley79)
    Well, as you said, the deteminant gives you the area SF. So how do we get a length scale factor from that?
    Square root of course! Thanks so much, I didn't realise you could do that.

    So was my assumption about the root 3 being scale factor wrong in all cases? Oh actually I guess that must only work when it written as

    (K 0)
    (0 k) because the determinant square root is still k. I think I get it now, thank you
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    (Original post by SamePrice)
    Square root of course! Thanks so much, I didn't realise you could do that.

    So was my assumption about the root 3 being scale factor wrong in all cases? Oh actually I guess that must only work when it written as

    (K 0)
    (0 k) because the determinant square root is still k. I think I get it now, thank you
    Yes thats right - it only works when it's just an enlargement - we've got another transformation in there ..

    Yes - remember GCSE ratio of similar areas, volumes etc?
    length ratio a:b gives area ratio a^2:b^2
 
 
 
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