Activity Description Learn about the vertical line test for functions by trying to connect points in the plane to build a function. When you have connected all of the points, you will be told if your graph is a valid graph of a function. Vertical Line Test is one of the Interactivate assessment explorers.

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Vertical Line Test

Place in mathematics curriculum:

This activity can be used to:

• practice students' function skills
• practice students' deductive reasoning skills
• familiarize students with the vertical line test for functions

This activity allows the user to attempt to build curves that pass the vertical line test, so that they are functions. This activity would work well in mixed ability groups of two for about twenty-five minutes if you use the exploration questions and ten minutes otherwise.

Preparations for this activity:

• give implicit directions on what they are to do. For example, "Today we are going to explore the world of functions ... we are going to make lines and test them... then we will try to answer the exploration questions..."
• answer the question "Why does the vertical line test work"?
• discuss functions, inputs, and outputs