inverse trig values and finding inverse

I have been having problems with these 3 problems and I'm looking for the answer and how it was obtained so I can make sense of what I need to do and what I've been doing wrong

finding the exact values of following expressions:

problem 1: inverse cos(cos(-4pi/7))

for problem 1 I've tried using the sum and difference formulas but I simply can't get to 4pi/7

problem 2: inverse sec(root 2)

for problem 2 I can't understand how to find out what the proper values are

problem 3 - find inverse of sin(x+2) -1

once again, boggled by how to do so

I appreciate any help, explanations and hints go a long way

thanks in advance