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#1 2012-12-10 08:13:24

zee-f
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Transformations

Hi,

I am really stuck on how to rotate the following

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


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

#2 2012-12-10 08:44:56

bob bundy
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Re: Transformations

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


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

#3 2012-12-11 02:26:16

zee-f
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Re: Transformations

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


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

#4 2012-12-11 05:27:12

bobbym
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Re: Transformations

Hi zee-f;

That is correct!


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

#5 2012-12-11 05:27:37

bob bundy
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Re: Transformations

hi zee-f,

That looks good to me,  smile

Bob


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

#6 2012-12-11 07:18:03

zee-f
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Re: Transformations

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

#7 2012-12-11 07:28:22

bobbym
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Re: Transformations

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.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

#8 2012-12-11 09:21:47

bob bundy
Moderator

Online

Re: Transformations

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


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

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