What information is marked in the diagram ?
-- The angles in the lower left corner of each triangle are
right angles, so the triangles are right triangles.
-- The angles in the lower right corner of each triangle are equal.
-- The slanted sides of both triangles are equal. (Since the triangles
are right triangles, the slanted sides are their hypotenees.)
If the hypotenuse and one acute angle of a right triangle are
equal respectively to the hypotenuse and one acute angle of
another right triangle, that's enough to prove that the triangles
are congruent.
