Answer:
it depends
Explanation:
The endpoints of the hypotenuse are insufficient to specify a right triangle. The perimeter can range from twice the distance between these points, about 18.868 units, to 1+√2 times the distance between these points, about 22.776 units.
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In the attached figure, the colored numbers are the total length of the two legs of that color. The hypotenuse and its length are in black.
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The distance between two points is given by the formula ...
d = √((x2-x1)^2 +(y2 -y1)^2)
The perimeter will be the sum of the distances between pairs of points that define the vertices of the triangle. We need to know the third vertex to answer the question precisely.