If quadrilateral ABCD rotates 90° counterclockwise about the origin, what are the coordinates of A′ in quadrilateral A′B′C′D′ ?

Question

bossvideogamer21 · Answer

If the coordinates of point B are (a,b),
 
then the coordinates of point B' are (-b,a).
 
 
               ^ y
B'             |
*–––––––-|
  \    -b     |
    \          |                            B
      \     a |                            |
        \      |                     /      |
          \    |             /           b |
            \  |      /                     |
              \|/________a______|___> x