In the set of straight lines in a plane, for the relation 'perpendicular' check whether it is reflexive, symmetric and transitive.

Explanation

To determine whether the relation 'perpendicular' among straight lines in a plane is reflexive, symmetric, and transitive, we will analyze each property step by step.

### Step 1: Check for Reflexivity
A relation is reflexive if every element is related to itself. In the context of lines, this means that a line must be perpendicular to itself.

- **Analysis**: No line can be perpendicular to itself because the angle between a line and itself is 0 degrees, and perpendicular lines must intersect at a right angle (90 degrees).

- **Conclusion**: Since no line is perpendicular to itself, the relation 'perpendicular' is **not reflexive**.
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