Illuminations: Rectangles and Parallelograms
Illuminations (National Council of Teachers of Mathematics)

Students use dynamic software to examine the properties of rectangles and parallelograms, and identify what distinguishes a rectangle from a more general parallelogram.

Illuminations: Discovering the Area Formula for Circles
Illuminations (National Council of Teachers of Mathematics)

Using a circle that has been divided into congruent sectors, students will discover the area formula by using their knowledge of parallelograms.

Illuminations: Finding the Area of Parallelograms
Illuminations (National Council of Teachers of Mathematics)

Students will use their knowledge of rectangles to discover the area formula for parallelograms.