ANSWER
The coordinates of the third vertices are or .
EXPLANATION
Let the hypotenuse of the right angle triangle have vertices and .
The third point is the intersection of the horizontal line that passes through (6,-2), that has equation and the vertical line that passes through which also has equation .
Hence one possible coordinates of the third vertex is .
The third vertex could also be the intersection of the vertical line that passes through (6,-2), that has equation and the horizontal line that passes through which also has equation .
Hence another possible coordinates of the third vertex is .
See diagram in attachment