In a diagram to mark that two lines are perpendicular, we put the following symbol:
in one of the angles that they form.
Also, if two lines are congruent, we mark them with the same symbol.
From the given diagram we get:
[tex]AC\perp BD,[/tex][tex]AD\cong CD\text{.}[/tex]
Answer:
19.- T.
20.- T.
21.- F.
