Education Technology

Sine and Cosine Identities

Published on 11/04/2008

Activity Overview

  • Students will explore the relationship between the measure of an angle and its sine and cosine.
  • Students will develop two trigonometric identities:
    sinA / cosA= tanA

    sin2A + cos2A = 1

  • Before the Activity

    Teacher preparation
    Download the attached .Doc documents and the TI_Nspire document. You will need to copy the .tns document to students' handheld before the exploration.
    Read activities in advance.

    During the Activity

    Classroom management tips:
    Be prepared to guide students during the exploration. Encourage students to look for patterns, make connections, and share their findings during the exploration.

    After the Activity

    Assessment and evaluation:

  • Evaluate students' conjectures written on pages 2.4 and 3.5 of their TI_Nspire document.
  • Students self evaluate their conjectures by testing them on pages 2.5 and 3.5 of their TI_Inspire documents.


  • Activity extensions
    Students can use fundamental trigonometric identities to simplify and rewrite expressions and to verify other identities.