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avatar+656 

I have an exam tomorrow, and I am really confused about this... 

here let's dive into the problem: 

for example (im just gonna make something up lol) 
we want to rotate the point (-2,3) 90 degrees counterclockwise...

we already know that if they tell us to rotate something 90 degrees, it means to rotate it in a counterclockwise direction

so then what would it mean to rotate something 90 degrees counterclockwise if normal 90 degrees is already counterclockwise....

if somebody can clarify this for me, i'd really appreciate it

thank you!!

 Oct 24, 2019
 #1
avatar+435 
+4

Wouldnt the points just return back to its original points, or am I mistaken?

 Oct 24, 2019
 #2
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+1

For a rotation 90 degrees around the origin, switch the coordinates for example if it is: (x,y) it will be: (y,x) notice that y became x and x became y values.

In your example, 

-2,3 will be 3,-2 

Speaking of counterclockwise 

Yes, if we rotate 90 degrees it is already in counterclockwise, It is just there to confuse you. 

 Oct 24, 2019
 #4
avatar+656 
0

wait wait wait,,, 

i agree with everything you just said except for one thing... 


shouldn't 90 degree rotations do this to a point?? 

\((x,y)\rightarrow(-y,x)\)


but thank you for your help :) your answer was extremely clear to understand. smiley

Nirvana  Oct 24, 2019
 #5
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+1

Ohh! You are right! 

(-y,x) is correct for 90 degrees

(Sorry I always get confused with 90 degrees and 270 lol) 

Guest Oct 24, 2019
 #6
avatar+656 
0

it's all good!! :) 
don't worry about it i know what you meant smiley

Nirvana  Oct 24, 2019
 #3
avatar+656 
0

thank you guys so much!!

 Oct 24, 2019
 #7
avatar+105674 
+1

If someone told me to rotate something by 90 degrees I would not know that I was meant to go counter clockwise. 

 

I would ask "which direction?"

 

I have never heard of that 'standard' assumption before. 

 Oct 25, 2019
 #8
avatar+656 
+1

idk, ngl i was pretty confused too when i first heard of that notation

but the teacher said like that's how it works in trig or something and that's how we will be doing it 

Nirvana  Oct 26, 2019
 #9
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+1

Think about the quadrants melody, they go counter clockwise

Guest Oct 26, 2019
 #10
avatar+105674 
+1

Yes I spos, I just had not seen that before. 

Melody  Oct 27, 2019

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