1. Exercise #15
Trigonometric Identities II
When LHS = RHS, the identity has been proved. Some common operations when
proving identities are:
1. Adding/Subtracting rational expressions
1 1
Ex.  2
cos  sin 
2
2. Multiplying/Dividing rational expressions
 1  1 
Ex.   2 
 cos   sin  
2
3. Factoring
Ex. sin   sin  cos 
3 2
4. Multiplying by the conjugate
1
Ex.
1  sin 

2. Examples
Prove each of the following:
tan   cot 
1.  2sin 2   1
tan   cot 
2. cos   tan  sin   sec

3. 3. sin  cos sec csc  1
1  tan 2 
4.  csc2 
tan 
2