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**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

Hi,

I am really stuck on how to rotate the following

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

One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,426

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

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

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

One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 87,228

Hi zee-f;

That is correct!

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,426

hi zee-f,

That looks good to me,

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

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

One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 87,228

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.

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,426

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

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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