How do you do Geometry the right way and what is the best way to remember how to do it?

Step-by-step explanation:

To understand geometry, it is easier to visualize the problem and then draw a diagram. If you're asked about some angles, draw them. Relationships like vertical angles are much easier to see in a diagram; if one isn't provided, draw it yourself.

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.