Alicia's Reflection #16

Alright well this week we learned identities and equations. At first it was really hard for me until I learned my trig identities. Here are the steps to solving these equations:

1. check identities
2. algebra
3. identities

These are the identities to memorize:

Reciprocal Relationships:

cscΘ=1/sinΘ
secΘ=1/cosΘ
cotΘ=1/tanΘ

Relationships with Negatives:

sin -Θ= -sinΘ and cos -Θ= -cosΘ
csc -Θ= -cscΘ and sec -Θ= -secΘ
tan -Θ= -tanΘ and cot -Θ= -cotΘ

Pythagorean Relationships:

sin²Θ+cos²Θ=1
1+tan²Θ=sec²Θ
1+cot²Θ=csc²Θ

Cofunction Relationships:

sinΘ=cos(90°-Θ) and cosΘ=sin(90°-Θ)
tanΘ=cot(90°-Θ) and cotΘ=tan(90°-Θ)
secΘ=csc(90°-Θ) and cscΘ=sec(90°-Θ)

***Cautions***

You cannot divide trig functions to cancel them

You can move everything to one side and factor out a trig function

You can divide by a trig function to create a new one


Helpful information:

I - II : make negative then add 180

I- III : add 180

I - IV : make negative then add 360

Sin- positive in 1 and 2... negative in 3 and 4

Cos- positive in 1 and 4. ..negative in 2 and 3

Tan- positive in 1 and 3... negative in 2 and 4


I could use some help with proving equations in section 8-4 if anyone has any helpful hints!!

Goodluck on the Chapter 8 Test tomorrow :)