Today we studies the Double Angle ID's: sin(2A)=2sinAcosA and cos(2A)=cos^2A-sin^2A. Once you solve for both sin(2A) and cos(2A), you can solve for tan(2A)=sin(2A)/cos(2A). It's important to know that for that the 2 in 2 sinAcosA isn't the same as the 2 in its equivalent sin(2A). Its derived from the sum of the 2A represented in the equation 2(sinAcosA).

12/2/09 Sum/Difference Identities

In class on December 2nd we learned about the Sum and Difference identities. (Note: a large portion of these notes show how we derived the identities given angles and prior knowledge of the unit circle.)

The identities allow us to find the sine, cosine, and tangent of angles we previously could not (ie: 15 degrees), by adding or subtracting (ie: 60-45=15) using angles for which we can already find the trig functions.

Coefficients of Angles (Trigonometry)

We discussed in class that normally when using trig identities to the meaasure of an angle, you come out with two possible angles. However, a coefficient of an angle produces that double that number of solutions.
girl in the hall: "It took me three minutes to get ready today"
MV: "I can tell"

Notes: 11/30

Sorry it took me this long to post the notes. I had a few problems. Anyway, today in class we learned how to solve trig equations by using 3 main steps:
1.Get the 1st answer from the inverse trig function
2.Then the second answer from the reflection of the trig ID (Ex: Tan= 180 or 2pie+the angle)
3.Add or subtract 2 pie or 360 (depending on whether you are in degrees or radians) to both of your answers from 1 and 2 to get as many answers as needed.