posted by willy .
Assume triangle JKL is in the first quadrant, with the measure of angle K = 90°. Suppose triangle JKL is a 45°-45°-90° triangle and segment JK is one of the legs. What are the coordinates of point L?
That triangle could be anywhere in the first quadrant and you have not told us the length of any side of the triangle.
and the answers are,
L could be 5 units to the right of K or to the left of K at the same level or y coordinate
so L could be (7,2) or L could be (-3,2)
However (-3,2) is not in the first quadrant