Quadrilaterals

∠1 + ∠2 + ∠3 + ∠4 = 360°

∠5 + ∠6 + ∠7 + ∠8 = 360°

In a parallelogram, opposite angles are equal

In a quadrilateral, if one pair of opposite angles is supplementary, the other pair is also supplementary

In a rectangle, each angle is 90°

Opposite sides of a parallelogram are equal

Diagonals of a parallelogram bisect each other

All sides of a rhombus are equal

Diagonals of a rhombus bisect each other at right angles

Diagonals of a rectangle are equal

DE = (1/2)BC and DE ∥ BC

Area = (1/2) × Base × Altitude

Area(triangle ADC) = (1/2) × DC × PD

Area(triangle ACB) = (1/2) × AB × QC