birectangular tetrahedron
This figure shows 3 faces of a tetrahedron, all 3 are right triangles. The fourth face is missing. You may drag point D on the right to fold or unfold these faces.
What can you tell about the missing face of this tetrahedron? What kind of triangle is it? How do you know?
If you change the side lengths of these faces (by dragging the green points on the left), what is still true about your description of the missing face?
What does the following note tell you about the faces of this tetrahedron?