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

1. (Original post by SamePrice)
So how do you find the SF of an enlargement from a matrix?
2. (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
3. (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?
4. (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?
5. (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?
6. (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
7. (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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