Answer:
180°
Step-by-step explanation: We are given the co-ordinates of ΔDEF as D(-1,6), E(1,3) and F(6,3).
Now, after rotation the co-ordinates of the new triangle D'E'F' are D'(1,-6), E'(-1,-3) and F'(-6,-3).
As we see that, the co-ordinates of triangle DEF are multiplied by negative sign to obtain the co-ordinates of triangle D'E'F'.
This means that, the triangle DEF is rotated 180° to form triangle D'E'F' because rotating 180 changes (x,y) to (-x,-y).
So, the rotation applied is 180° to ΔDEF.
