Lesson Plan

The Definition of Sine, Cosine, and Tangent

Curated and Reviewed by Lesson Planet

Introduce your classes to a new world of mathematics. Pupils learn to call trigonometric ratios by their given names: sine, cosine, and tangent. They find ratios and use known ratios to discover missing sides of similar triangles. 

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CCSS: Designed
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Instructional Ideas
  • Compare the trigonometric ratios of special right triangles with the known patterns; help learners to see that they can apply this concept to all right triangles
  • Form collaborative groups to complete the exit ticket and possibly the practice problems
Classroom Considerations
  • Pupils should already have a basic understanding of side ratios in right triangles
  • Builds from the previous lesson in the 36 part series
  • Lesson does not require a calculator as the focus is on similarity and equivalent ratios
  • The well-designed lesson leads students through the process of applying trigonometric ratios to similar triangles
  • Makes a connection to the sine and cosine of complementary angles
  • There are inconsistencies in simplifying radicals; sometimes the denominator is rationalized and other times it is not