Trigonometric Identities: Negative Angle Relations

[smetrop]

I'm trying to figure out how these identities were formed. If someone could explain how they work or where they come from I would appreciate it. Thank you.

sin (-A) = -sin A
cos (-A) = cos A
tan (-A) = -tan A

 

[tkhunny]

Have you met the definitions of these functions on the Unit Circle? Such an observation makes the relations shown immediately obvious.

Sine and Tangent are Odd functions.
Cosine is an Even function.

Look up the definitions of "Odd Function" and "Even Function" and you should see it.

 

[smetrop]

I need to know how it relates to angles though. I looked up the even-odd functions but it didn't say where the angle comes into play.

 

[Deleted member 4993]

I need to know how it relates to angles though. I looked up the even-odd functions but it didn't say where the angle comes into play.

You need a face-to-face tutor. May be your class teacher can walk you through it. This needs concept review - not easily done long-distance....

 

[tkhunny]

I need to know how it relates to angles though. I looked up the even-odd functions but it didn't say where the angle comes into play.

Yes it did. It is exactly what is needed to answer your question. The fact that you don't see it underscores Subhotosh's advice. Please pursue it aggressively. See your academic advisor.