For the function y=sin−1(x−1)+cos−1x−1 to be defined, all parts must work.
The function sin−1 only accepts inputs between −1 and 1 (inclusive).
For sin−1(x−1):
−1≤(x−1)≤1
−1+1≤x−1+1≤1+1
0≤x≤2
From the first term: x∈[0,2]
For cos−1x−1, there are two conditions:
The square root must be real (non-negative radicand):
x−1≥0
x≥1
The function cos−1 only accepts inputs between −1 and 1.
Since square roots are always non-negative:
0≤x−1≤1
x−1≤1
x−1≤1
x≤2
Combining both conditions: 1≤x≤2
From the second term: x∈[1,2]
For the entire function to be defined:
First term requires: [0,2]
Second term requires: [1,2]
The intersection is: [1,2]
Therefore, the domain is [1,2].