Question

Name or state the postulate, definition, or theorem that justifies each statement about the diagram.

If $\overleftrightarrow{DA}\perp \overleftrightarrow{AB}$, then $m\angle DAB=90°$.

Short answer

Definition of perpendicular lines is used to justify the statement.

Step-by-step solution

Step 1. Identify the angle between the given lines.

Observe that the lines $\overleftrightarrow{DA}$and $\overleftrightarrow{AB}$ forms the angle $\angle DAB$.

Step 2. Determine the definition or concept that can be used.

Perpendicular Lines: Two lines which intersect each other to form right angle$(90°)$are called perpendicular lines.

Step 3. Apply the concept.

By the definition of perpendicular lines, and intersect each other at right angles.

Therefore, $m\angle DAB=90°$.