A
E
B
Point
is the vertex of the angle marked in the figure.

Point E

Step-by-step explanation:

A vertex can be described as an angle formed when two lines intersect or join together. In the figure given, point E is the intersection point.

The point that is referred to as the vertex of the marked angle where the two lines intersect is point E.

Point E is the vertex of <BEC.

last option

step-by-step explanation:

given that δdef is right and isoceles,

assuming that side df is the hypotenuse means that de an ef are the other 2 sides that intersect at 90° and are of equal length.

because they are of equal length, we can say that they are congruent

because they intersect at 90°, their slopes must be opposite reciprocals.

only the last option satisfies these conditions.

2.83941151 would be the answer you're looking for! : )