Definition: A rectangle is quadrilateral with 4 right angles (90°). Rule: Opposite sides of a rectangle are congruent (of equal length). Proof: By the definition of a rectangle, it follows that every rectangle is a parallelogram. We showed that opposite sides of a parallelogram are congruent. It follows that opposite sides of a rectangle are congruent. Interactivity 1: Rectangles Directions for interactivity Click and drag the slider buttons to change the size. Click and drag point B to move and point А to rotate. 
Basic formulas for rectangles with sides a and b: the perimeter is: L=2(a+b) , and the area is: A=ab .
Examples for perimeter and area of rectangles Check the following examples using the above interactivity.

Interactivity 2: Construct a rectangle

Equivalent definition:
Theorems
The diagonals of a rectangle are congruent (the same length) Interactivity Get the latest Java Plugin here.

Related themes:
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