Quick Review An identity is an equation that is true for all values of the variable. Some basic identities are:
To prove that an identity is true: change either side, or both sides, until the sides are the same. Example 1 csc =
I would work with the right side. Try to get it to look like the left side. Change cot
to sin and cosine s. You have now proved the identity!
Example 2 sec  sec
sin^{2}
= cos
I would work with the left side. Factor out a sec . sec (1  sin^{2} ) = cos Since sin^{2} + cos^{2} = 1, So, sec (cos^{2} ) = cos Example 3
