RUME 28
2026
Alexandria, Virginia
Students’ Mathematical Reasoning About the Period of the Sum of Trigonometric Functions
Page: 668
This study investigates students’ mathematical reasoning when determining the period of the sum of two cosine functions through exploratory teaching interviews. Two undergraduate students engaged with Desmos applets to explore the sum of two cosine functions. The analysis revealed output-oriented reasoning that focuses on identifying input values where function output repeats, and alignment-oriented reasoning that focuses on where the period of the sum function aligns with the periods of individual trigonometric functions to determine the period of a sum of two trigonometric functions.