You can
put this solution on YOUR website!C(3,-2). The triangle is rotated 90 degrees counterclockwise. Use the rotation matrix [0 -1][1 0] (please note that [1 0] is directly under [0 -1] but I do not have large enough brackets or the know-how to place it like that)to find the coordinates of C'.
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[0..-1]
[1...0]
times
[3]
[-2]
C' =
[2]
[3]
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You can check this out visually by plotting (3,-2),
sketching a circle thru that point with center at
the origin, then extimate a counter-clockwise
rotation of 90 degrees. Do you end up at (2,-3)?
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cheers,
Stan H.