# Trigonometry - Addition and subtraction formulas

1. $sin(\alpha+\beta)=sin\alpha.cos\beta+sin\beta.cos\alpha$

2. $sin(\alpha-\beta)=sin\alpha.cos\beta-sin\beta.cos\alpha$

3. $cos(\alpha+\beta)=cos\alpha.cos\beta-sin\alpha.sin\beta$

4. $cos(\alpha-\beta)=cos\alpha.cos\beta+sin\alpha.sin\beta$

5. $tan(\alpha+\beta)={{tan\alpha+tan\beta} \over 1-tan\alpha.tan\beta}$

6. $tan(\alpha-\beta)={{tan\alpha-tan\beta} \over 1+tan\alpha.tan\beta}$

7. $cot(\alpha+\beta)={ 1-tan\alpha.tan\beta \over {tan\alpha+tan\beta} }$

8. $cot(\alpha-\beta)={ 1+tan\alpha.tan\beta \over {tan\alpha-tan\beta} }$