Hey there!!
Always remember this :
90-degree counterclockwise: (x, y) → (-y, x)
180-degree counterclockwise: (x, y) → (-x, -y)
270-degree counterclockwise: (x, y) → (y, -x)
1st quadrant : ( x , y )
second quadrant : ( -x , y )
Third quadrant : ( - x , - y )
Fourth quadrant : ( x , -y )
Now, the triangle abc lies in the 1st quadrant. So, all the vertexes will have positive values.
Let's take the vertex a as ( 1 , 2 )
Vertex b as ( 4 , 7 )
Vertex c as ( 5 , 9 )
If we rotate these values in 90 degress angle, these would become ( -y , x )
Vertex a : ( 1 , 2 ) ; After rotating : ( -2 , 1 )
Vertex b : ( 4 , 7 ) ; After rotating : ( -7 , 4 )
Vertex c : ( 5 , 9 ) ; After rotating : ( -9 , 5 )
Hope my answer helps!
