Construction of Equilateral Triangle - STD 9 - Page 39.1 Teaching Aid

Equilateral Triangle • Perimeter 11 cm (Parallel Lines Method)

Equilateral Triangle Construction

Perimeter = 11 cm • Using Parallel Lines Division Method

This construction uses the Parallel Lines Theorem: When three or more parallel lines cut two transversals, they divide the transversals in the same ratio. Here we use it to divide the 11 cm segment into three equal parts.
Construction Figure
AB = 11 cm (Perimeter)
Each side of Δ = 11/3 cm ≈ 3.67 cm
STEP-BY-STEP CONSTRUCTION

Interactive Guide

STEP 1/8
Why Parallel Lines?
To divide 11 cm into three equal parts without measuring 11/3 directly.
Result
You get an equilateral triangle with all sides exactly 11/3 cm and perimeter exactly 11 cm.
Key Theorem Used
"Parallel lines cut transversals proportionally" (Basic Proportionality Theorem)