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  1. It is then reflected vertically in y = 6.
  2. It is then rotated 90 in a clockwise direction from the bottom right-hand corner. (Context is shown in the picture below)

I don't understand why these prepositions are used.

For (1), a line(y=6) doesn't have internal space, so why "in"? Shouldn't it be :...reflected across y= 6.

For (2), I think it should be "to rotate on or around" rather "rotate from".

 Primary maths 5

1 Answer 1

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The first is idiomatic, and follows the physical example of "reflect in a mirror". English already used "in" for this, probably because your reflection appears to be "in" a space behind the mirror. And the idiom was then carried over to the geometric notion of "reflection in a line".

For rotate, "about" or "around" would also be correct. The use of "from" conforms with the preposition used for the fixed point in enlargements.

What a peculiar context for a transformations question! Who in their right mind would specify a landing area in terms of a square that has been translated, reflected and rotated... and the term "bottom right hand corner" is pretty ambiguous - does it mean the right hand corner of the square (before or after reflection?), or of the grid. If the square, bottom only makes sense in the drawing, since it is actually a horizontal square - Think about it, that's a map so a shape on the map has no bottom, only a north, south, east and west

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  • As an American English speaker I am surprised to see "reflect...in y = 6". This page uses "over" and "across".
    – nschneid
    Aug 6, 2023 at 12:34
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    I'll tag this as british, then. Would you use "over" when talking about reflections in a physical mirror? "I saw my face reflected over the mirror"
    – James K
    Aug 7, 2023 at 1:44
  • @nschneid The book is Oxford International Primary Math, Oxford University Presss. So it might be a british thing.
    – ForOU
    Aug 7, 2023 at 2:45
  • @JamesK no. Things are reflected in mirrors. But a line is a 1-dimensional object so it's odd for me to think of something being "in" it.
    – nschneid
    Aug 7, 2023 at 4:59

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