"I Saw the Sine"

Before:

1. As the students enter the classroom, the Bell Ringer should be posted on the interactive whiteboard (The bellringer can be found on the first slide of the PowerPoint).
2. Select students at random to answer the bell ringer. (Answers: Hypotenuse is 5, one leg is 3 and the other leg is 4.)
3. Introduce the video from Khan Academy (“Basic Trigonometry”)
4. The teacher can stop the video for questioning and comprehension.

During:

1. After the video, the teacher should introduce the saying “sock-a-tow-a” (SOH-CAH-TOA).
2. Show the students how to use the calculator to find sine, cosine, and tangent. Press the trig ratio key and then the angle.
3. Use the calculator to find the angle from the decimal form of the trig ratio. Press INV key then trig ratio key.
4. Explain that the letters in front stand for a particular trig ratio of the right triangle.
   1. S – sine
   2. C – cosine
   3. T – tangent
   4. O – opposite side of the given angle
   5. A – adjacent side of the given angle
   6. H – hypotenuse
   7. Use the Bell Ringer and given the bottom angle to write the trig ratios in fraction form and decimal form.
      1. 3/5 and 0.6 are the Sine using the bottom angle
      2. 4/5 and 0.8 are the Cosine using the bottom angle
      3. Show the video “Writing the ratios for sine, cosine, and tangent”.
      4. Using the angles of a right triangle, show the students that the two angles will be acute. The sum of the two acute angles must be 90 degrees, which makes them complementary.
      5. Using the definition of proportions, the sine of one acute angle will equal the cosine of the other acute angle
      6. The students will make a table and compare ratios.

From the bell ringer triangle…Draw the triangle on the smart board

Students compare ratios: sine x = cosine y

Students compare ratios: cosine x = sine y

The students have proven that the trig ratios (sine/cosine) of opposite complementary angles of a right triangle are equal.

After:

1. Assign the problems from the PDF worksheet.
2. The teacher can upload the worksheet in Google classroom, then the students can access it and submit the answers.
3. If the teacher does not have access to technology, then he/she will need to make copies for each student.
4. The students will complete the worksheet for homework.

Exit Slip

As the students begin the assignment, place the second slide from the PowerPoint on the smart board. Ask the students to complete the problem on their own paper and turn it in as they leave the classroom.