Is a Square a Rectangle?

We started another mini geometry unit today: square and rectangles.

First, we investigated characteristics of square and rectangles.  We decided:

Rectangles

• have four 90° angles
• opposite sides are the same length
• opposite sides are parallel

Squares

• have four 90° angles
• all four sides are the same length
• opposite sides are parallel (from which we deduced that the lines must be straight)
• is a rectangle

This last feature about squares brought this question forth:

The students discussed this and came up with some very valid answers.  They should good critical thinking skills and through debate and discussion were able to decipher that this statement is true and why it is so.