Basic Proportionality Theorem

If a line is drawn parallel to one side of a triangle to intersect the other two sides in distinct points, the other two sides are divided in the same ratio.

Measurements

AD: -

DB: -

AE: -

EC: -

BC: -

DE: -

DE₁: -

AE₁: -

E₁C: -

Ratio Verification

AD/DB

-

AE/EC

-

AE₁/E₁C

-

Show Line E→F (parallel to AC)

Show Line E₁→F₁ (parallel to AC)

Interactive Controls

Position of D

Drag to move point D along AB

Triangle Type