Question

Rotate a right triangle with points 2,3 4,7 5,4 90 degrees to the vertex point 2,3.

Answer 1

Is it 2,3 -2,5 1,6?

Answer 2

Your post: Rotate a right triangle with points 2,3 4,7 5,4 90 degrees to the vertex point 2,3.

rephrased:
Rotate a right triangle with points (2,3), (4,7), and (5,4) by 90° about the vertex point (2,3) counterclockwise .

Your answer is correct, I am curious what method you used.

Answer 3

(x,y)→(2-(y-3),3+(x-2)) = (5-y,1+x)

Answer 4

I put perpendicular lines through the vertex point and rotated it