# Mathematics: Establishing Trigonometric Identities

Title: Establishing Trigonometric Identities
Discipline(s) or Field(s): Mathematics
Authors: Kavita Bhatia, Jinbo Lu, LaVerne Harrison, University of Wisconsin – Marshfield/Wood County
Submission Date: January 1, 2011

Executive Summary: Our goal was to help students to understand the process of establishing identities and to carry out the process effectively.

In establishing an identity, students have to apply a series of logical steps, while always keeping their objective in mind. There is no template problem, no recipe to follow. The steps for establishing an identity are unique to that identity. Our focus was on teaching students what constitutes the proof of an identity and how to present the proof in logical steps.

In designing the lesson we tried to link students’ prior knowledge about algebra, in particular algebraic equations and rational equations, with trigonometric functions. To emphasize this we began the lecture by first establishing an algebraic identity, followed by the replacement of the present variable with a trigonometric function to obtain a trigonometric identity. Other examples of identities were then proved on the board with each step being provided by a different student and the underlying algebra underscored by the instructor. Finally the students were given a worksheet with different types of identities to work on as the instructor observed and answered questions.

There were six identities on the worksheet. Most students attempted 4 ~ 5 and on average completed the proofs of about 4 identities correctly, using varied approaches. Furthermore, the students displayed enthusiasm and confidence in carrying out their work. This carried over to their performance in the final exam: more students attempted and successfully established the identities compared to previous years, when a majority of the students simply skipped these problems.

Mathematics: Establishing Trigonometric Identities – The Study (Final Report)

# Mathematics: Calculating the Distance Between a Point and a Line

TItle: Calculating the Distance Between a Point and a Line – by Hand and Using TI-89/TI-Voyage 200 Calculator Technology
Discipline(s) or Field(s): Mathematics
Authors: Theresa Adsit, James Meyer, Gary Wardall, University of Wiscnsin-Green Bay
Submission Date: December 12, 2007

Executive Summary

The lesson topic is the distance between a point and a line using an algebraic approach and a calculator based approach to problem solving.

Learning Goals: The immediate academic learning goals of this lesson were to develop students’ understanding of the derivation of the point to line distance formula and to develop the ability to apply the point to line distance formula to solve problems. The ongoing academic learning goals of this lesson were to develop the ability to use the calculator to build structures to solve problems involving systems of equations, to develop a greater understanding of the similarities between calculators and other forms of technology, and to further develop strategies for solving multi-step problems.

Instructional Design: The lesson was divided into five steps. The first step was instructor led and involved the determination of the shortest distance between a specific point and a specific line using the techniques of algebra and paper and pencil. The second step mimicked the first but rather than using paper and pencil the instructor and students used either a TI-89 or TI-Voyage 200 calculator. During the third step of the lesson the instructor and students then developed the point to line distance formula for any point and any line using the TI-89 or TI-Voyage 200 calculator. The fourth step of the lesson involved the students verifying the formula by using the developed formula along with the point and the line from parts one and two to determine if the developed formula did indeed yield the same results as their previous calculations. Finally, in step five the students worked collaboratively and then independently on an assignment related to the lesson.

Major Findings about Student Learning: The students with the assistance of the instructor were able to build the appropriate structures using either a TI-89 or TI-Voyage 200 calculator to solve a problem involving systems of equations and to derive a formula involving systems of equations. The students were collaboratively and individually able to apply the developed formula to other problems in the assignment. Students questioned each other and the instructor more often during the collaborative work period than during the instructor led portion of the lesson. Some students did have an underlying misunderstanding of the benefits of a formula.