The three identities below are all called pythagorean identities. the second and third follow from the first, as you
saw in example 1 and the exit ticket.
a. for which values of θ are each of these identities defined?
i. sin2(theta) + cos2(theta) = 1, where the functions on both sides are defined.
ii. tan2(theta) + 1 = sec2(theta), where the functions on both sides are defined.
iii. 1 + cot2(theta) = csc2(theta), where the functions on both sides are defined.
b. for which of the three identities is 0 in the domain of validity?
c. for which of the three identities is

2 in the domain of validity?
d. for which of the three identities is −
4 in the domain of validity?