Discovering Trig

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Students will be able to identify sine, cosine and tangent ratios using three similar triangles.

Big Idea

It's trig time! Students will use a hands-on activity to discover ratios in right triangles like sine, cosine and tangent.

Do Now

10 minutes

For this lesson Do Now, students review finding right triangle side lengths  using the Pythagorean theorem.  Activating this prior knowledge will prepare students to persevere through a challenging discovery similar triangle centered activity as they engaging in repeated reasoning to determine the sine, cosine and tangent trigonometric ratios (MP 1 and MP 8).  The CCSS Geometry curriculum only focuses on right triangle trigonometry so this unit might be well placed after a similar triangle and/or shapes unit. 

Getting Triggy with It

5 minutes

In order to get students excited about the start of this trigonometry unit, teachers can show this video.  The video highlights some important topics that will be studied in this unit, like sine, cosine and tangent.  The video shows a high school in Ohio re-creating the Will Smith song to "Getting Triggy with It."  You can find a copy of the Lyrics for Getting Triggy with It for students here. 

Discovery of Trig Ratios

50 minutes

Activity/Homework and Exit Ticket

15 minutes

Students may still need time to finish the activity at the end of class but if time remains, they can start the Homework - Discovering Trig which includes review questions from the Regent's Prep website that focuses on similar triangles.

Students can complete question #1 from the homework assignment, as an exit ticket. The question has students  write an email to a classmate who is absent, explaining how we discovered sine, cosine and tangent using similar triangles.