Given: Rectangle ABCD, CF ⟂ BD

Prove: AD / EC = AB / ED

Click or touch to draw on the diagram
AA similarity
Perpendicular lines form right angles
AD / EC = AB / ED
Definition
∠DEC = ∠A
Rectangle ABCD, CF ⟂ BD
∠ABD = ∠CDE
Given
Definition
Parallel lines form equal alternate interior angles
∠A is a right angle
ABCD is a parallelogram
AB ǁ CD
Definition
△DAB ~ △CED
∠DEC is a right angle
All right angles are equal
All rectangles are parallelograms