Rotate the triangle 90° anti-clockwise about the cross.

Answer:
see below
Step-by-step explanation:
-90 degrees, the rule is (x, y) --------> (-y, x)
The leftmost point is at (1,1) so it will be at (-1, 1)
The top right point is at (4,1) so it will be at (-1,4)
The bottom right point is at (4,-1) so it will be at (1,4)