Addition Formulas for Trigonometric Functions

Trigonometric Functions , ,

Consider the angle , with the terminal side of the angle intersecting a circle centered at the origin with radius at the point :

Trigonometric Identities Based on

1. Identity:
   Starting from , divide both sides by ( ):
   
2. Identity:
   Starting from , divide both sides by ( ):
   

Addition Formulas for Trigonometric Functions

1. Sine Addition and Subtraction
   
   
2. Cosine Addition and Subtraction
   
   
3. Tangent Addition and Subtraction