page+27


 * Aim: How do we find the sine of the difference of two angles and the sine of the sum of two angles?** //(These formulas will be on the Regents Reference sheet)//

By the end of the lesson, you will be able to...
 * 1) verify the validity of the formula for the sine of the difference of two angles
 * 2) verify the validity of the formula for the sine of the sum of two angles
 * 3) apply the formulas for sin(A - B) and sin (A+B) to find the exact value of expressions involving angles measured in radians and in degrees
 * 4) state the sum and difference formulas in words

Before you begin watching the videos, copy down the following questions into your notebook. Answer them as you watch the video.


 * 1) What is the sine sum formula?
 * 2) What is the sine difference formula?
 * 3) How does the sine sum formula differ from the cosine formula?
 * 4) How does the sine difference formula differ from the cosine difference formula?

[|Video 1]

[|Video 2]


 * **Classwork:** Solve each problem using the sine sum or sin difference formulas.


 * 1) Find the exact value of sin 15 degrees. (Ans: (sqrt6 - sqrt2)/4)
 * 2) Show that sin (pi + c) = - sin c


 * **Homework:** Do numbers 3-21 in multiples of 3.

[|Sine_Sum_and_difference.JPG]


 * **Answers**

[|A-Sine_sum_and_diff.JPG]


 * **Journal entry:** How can we use the formulas today to derive the formula for sin (A + B + C)?