A triangle has coordinates A (1, 5), B (-2, 1) and C (0, -4). What are the new coordinates if the triangle is rotated 90° clockwise around the origin?

Question

anonymous · Answer

@tkhunny

tkhunny · Answer

Youshould have no trouble at all finding C'.  What is it?

anonymous · Answer

-4,0)

tkhunny · Answer

This should give you a clue.  Just look at it in your mind.  You should be able to see it.

(0,-4) ==> (-4,0)
(3,2) ==> (-2,3)

Looks to me like x and y change places and one of them changes sign.  Can you formulate a general rule?

anonymous · Answer

that makes this sound easier
so a is going to be (5,-1)

tkhunny · Answer

Only B' remains.

anonymous · Answer

and b is (1,2)

tkhunny · Answer

That's about it.  Good work.

anonymous · Answer

thanks for showing me what i was missing, i just got into rotation and stuff and for some reason i got verry confused with this question

tkhunny · Answer

You can formalize it

x' = y
y' = -x

Is that it or did I miss it?

anonymous · Answer

i think you got it

tkhunny · Answer

How about GENERALIZE it?

x' = xcos(a) - ysin(a)
y' = xsin(a) + ycos(a)

What happens when you use a = -90º?