An equilateral triangle has a side length of $a$. What is the total number of lines of reflectional symmetry possessed by this triangle?

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### 1. Strategy & Theoretical Principles For any regular polygon with $n$ sides: - Number of lines of reflectional symmetry = $n$. - For an equilateral triangle ($n = 3$), each line of symmetry passes through one vertex and the midpoint of the opposite side (perpendicular bisector / altitude / median). ### 2. Analytical Verification Since there are 3 distinct vertices, there are exactly **3** lines of reflectional symmetry. ### 3. Distractor Forensics - A scalene triangle has 0 lines of symmetry; an isosceles triangle has 1; an equilateral triangle has 3. ### 4. Exam Trap & Standard Reference - **Trap Alert:** Regular $n$-gons have exactly $n$ axes of symmetry. - **Standard Reference:** GATE General Aptitude Official Syllabus - Spatial Aptitude.

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