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In the rectangular coordinate system above, the line y = x [#permalink]
27 Dec 2012, 04:05

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A

B

C

D

E

Difficulty:

25% (low)

Question Stats:

71% (02:27) correct
29% (01:38) wrong based on 209 sessions

Attachment:

Reflcetion.png [ 8.39 KiB | Viewed 2467 times ]

In the rectangular coordinate system above, the line y = x is the perpendicular bisector of segment AB (not shown), and the x-axis is the perpendicular bisector of segment BC (not shown). If the coordinates of point A are (2,3), what are the coordinates of point C ?

Re: In the rectangular coordinate system above, the line y = x [#permalink]
27 Dec 2012, 04:13

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Expert's post

In the rectangular coordinate system above, the line y = x is the perpendicular bisector of segment AB (not shown), and the x-axis is the perpendicular bisector of segment BC (not shown). If the coordinates of point A are (2,3), what are the coordinates of point C ?

Since the line y=x is the perpendicular bisector of segment AB, then point B is the mirror reflection of point A around the line y=x, so its coordinates are (3, 2). In any mirror reflection around the line y = x, the x-coordinate and the y-coordinate of a point become interchanged.

The same way, since the y-axis is the perpendicular bisector of segment BC then the point C is the mirror reflection of point B around the y-axis, so its coordinates are (-3, 2). In any mirror reflection around the x-axis, the x-coordinate remains the same, and the sign of the y-coordinate changes.

Answer: D.

The question becomes much easier if you just draw a rough sketch:

Attachment:

Reflection2.png [ 10.75 KiB | Viewed 2334 times ]

Now, you can simply see that only D can be the correct answer.

Re: In the rectangular coordinate system above, the line y = x [#permalink]
30 Oct 2013, 05:25

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From question stem, we can know that, Point C will be in the 4th quadrant (X,-Y), which comes down to option C&D. B is perpendicular to A (2,3). Hence co-ordinates of B will be (3,2). C & B are parallel to Y-axis and are on the same line. Hence co-ordinates of C will share same X-co-ordinate. (3,-Y). i.e. Ans. choice D

*I have difficult time understanding Co-ordiante geometry, hence try to solve in the simple way. This was my approach and was able to get ans. in less than a Minute.

gmatclubot

Re: In the rectangular coordinate system above, the line y = x
[#permalink]
30 Oct 2013, 05:25