How do you get (-square root 2) from csc(7pi/4)

Show all steps and explain. According to the table I have memorized csc(pi/4) = square root 2.

For trigonometry, you should memorize sin and cos for
pi, 2pi
pi/2, 3pi/2
pi/3, 2pi/3, 4pi/3, 5pi/3
pi/4, 3pi/4, 5pi/4, 7pi/4
csc(7pi/4) =
1/sin(7pi/4) =
1/(-1/√2) =
-√2