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## Topic review (newest first)

bob bundy
2012-12-11 09:21:47

hi zee-f

I call it an enlargement but it is the same as a dilation.

I made a triangle ABC.

Then I made it bigger  = DBE

The angles stay the same.

Bob

bobbym
2012-12-11 07:28:22

Hi;

The sides are dilated by a common factor but the ratios of the sides remain the same. In plain english the triangle will look the same just bigger.

zee-f
2012-12-11 07:18:03

I choose B and it was incorrect but why doesn't the angle change because  the size is getting bigger.

1. An angle changes in size as it undergoes a dilation.
A False
BTrue

bob bundy
2012-12-11 05:27:37

hi zee-f,

That looks good to me,

Bob

bobbym
2012-12-11 05:27:12

Hi zee-f;

That is correct!

zee-f
2012-12-11 02:26:16

I rotated the paper  270 clock wise so 3 times clockwise and I got

bob bundy
2012-12-10 08:44:56

hi zee-f

When you rotate 270 clockwise, that's the same as 90 anticlockwise.  (90, 180, 270, 360)

Look at the point (2,1)  I've boxed it into a rectangle and then showed the whole rectangle rotating.

That corner moves to (-1,2)  For 90 degrees that sort of thing always happens.  The x and y coordinates swap over and one becomes negative.

It happens because the across distance in the rectangle becomes the up distance and the up becomes the across (but now going to the left ... ie. it is now a negative amount).

2 ----> -1
1 ---->  2

So you should be able to do the other points the same way.

Bob

zee-f
2012-12-10 08:13:24

Hi,

I am really stuck on how to rotate the following

Rotate the triangle 270 clockwise around (0,0).