Given that the point B is (1,1) is rotate 90° counterclockwise around the origin.
We need to determine the coordinates of the resulting point B'.
<u>Coordinates of the point B':</u>
The general rule to rotate the point 90° counterclockwise around the origin is given by

The new coordinate can be determined by interchanging the coordinates of x and y and changing the sign of y.
Now, we shall determine the coordinates of the point B' by substituting (1,1) in the general rule.
Thus, we have;
Coordinates of B' = 
Thus, the coordinates of the resulting point B' is (-1,1)