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Showing 1 question in Mathematics for Class 10. Tap a card to reveal the answer.
MathematicsTrianglesmediumState the Basic Proportionality Theorem (Thales' theorem).
Reveal answer ↓
What it is
A line parallel to one side of a triangle cuts the other two sides in the same ratio.
Answer
The Basic Proportionality Theorem states that if a line is drawn parallel to one side of a triangle to intersect the other two sides at distinct points, then it divides those two sides in the same ratio. In triangle ABC, if DE is parallel to BC and meets AB at D and AC at E, then AD/DB = AE/EC.
If DE || BC then AD/DB = AE/EC
- •Line parallel to one side of a triangle
- •Divides the other two sides in the same ratio
- •AD/DB = AE/EC
- •Basis of similarity of triangles
Why learn this
It's the basis of similarity, scale drawings, maps and finding heights from shadows.
💡 Memory trick
Parallel line inside a triangle -> equal ratios: AD/DB = AE/EC.