PreCalc Unit 5 Trig Identities, Equations.notebook

1

January 03, 2019

Jul 26­11:59 AM

5.4 Sum and Difference Identities

Lesson Objectives:

1) I can use sum & difference identities to evaluate trigonometric functions

2) I can use sum & difference identities to solve trigonometric equations

Jul 26­11:59 AM

(pass) interference: If your TV's picture is blurry or your radio tunes into static & garbled voices, the problem is most likely due to interference. Interference happens when waves pass through the same space at the same time (can't happen with matter, as basically every sci­fi time travel movie EVER explains). We can use Trig Identities to determine the type of interference taking place.

PreCalc Unit 5 Trig Identities, Equations.notebook

2

January 03, 2019

Jan 3­12:47 PM

Jan 3­12:50 PM

PreCalc Unit 5 Trig Identities, Equations.notebook

3

January 03, 2019

Jul 26­11:59 AM

Find the exact value of each trig expression:sin 15° tan 7π 12 cos 15° sin 5π 12

If you write angle measures as the sums/differences of special angle measures, you can use the sum/difference identities to find exact values of less common angles.

Jul 26­11:59 AM

We can also use sum/difference identities to solve real­world problems like this:ELECTRICITY An alternating current i in amperes in another circuit can be found after t seconds using i = 2 (sin 285)t, where 285 is a degree measure. A) Rewrite the formula in terms of the difference of two angle measures; B) Use a sine difference identity to find the exact value after 1 second.

PreCalc Unit 5 Trig Identities, Equations.notebook

4

January 03, 2019

Jul 26­11:59 AM

Rewrite (S/D Identity) as a Single Trig FunctionFind the exact value of

Simplify:sin x sin 3x ­ cos x cos 3x

cos cos + sin sin