Answer:
first blank: 15
second blank: 90
Explanation:
Obviously, sin and cos are related, but they are not the same thing. In order for them to be equal:
sin(____) = cos(75)
the angles have to add up to 90 (complementary)
What + 75 is 90?
Do a tiny calc:
90 - 75 is 15
The second question is stating the rule generically.
x + (90 - x) is 90