Formative Assessment 107

Assessment Problem: 

Students are given a worksheet in a dynamic geometry package.  The construction, hidden from the students, is as follows: given two points A and B, construct the line through them.  Take a third point, P, and construct H, the foot of the perpendicular from P to line AB.  Students can drag any of the points.  The problem is to determine the relationships among the points.  Follow-up: When are two functions equal?

Mathematical Issues: 

Students struggle with the standard definition of function. This exercise gives students a chance to explore the idea of a function without algebraic symbolism confounding the issue. They directly see covariation by moving one point and seeing how the others react.

Domain: 
Patterns & Functions
Theme: 
Functions
Common Core Standards: 
F-BF: Building Functions
Technology: 
Geometer's Sketchpad, Geogebra
Research References: 
Falcade, R., Laborde, C., & Mariotti, M. (2007). Approaching functions: Cabri tools as instruments of semiotic mediation. Educational Studies in Mathematics, 66(3), 317-333.