If the domain of the function f(x)= cos^-1√x^2-x+1 √ sin^-1( 2x-1 2) is the interval (α ,β ], then α +β is equal to:
JEE Main 2021 — Mathematics Algebra
2021mcqmedium
If the domain of the function f(x)=sin−1(22x−1)cos−1x2−x+1 is the interval (α,β], then α+β is equal to:
Official previous-year question
Held on 22 Jul 2021 · Verified 6 Jul 2026.
Options
A
23
B
2
C
21
D
1
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Solution
Given function is f(x)=sin−1(22x−1)cos−1x2−x+1
For, {\mathrm{sin}}^{-1}x&{\mathrm{cos}}^{1}x to be defined −1≤x≤1 and for f(x) to be defined f(x)≥0 and the denominator of any expression can never be zero.
Thus, to define the domain of the given function, we have
−1≤x2−x+1≤1,x2−x+1≥0 and sin−1(22x−1)>0
Taking the common values and using the range of sin−1x i.e. for positive values 0<sin−1x≤2π, we get
0≤x2−x+1≤1 and 0<sin−1(22x−1)≤2π
⇒x2−x≤0 and 0<22x−1≤1
⇒x(x−1)≤0 and 0<2x−1≤2
⇒x∈[0,1] and 1<2x≤3
⇒x∈[0,1] and 21<x≤23
Now, taking intersection, we get x∈(21,1]
Given, domain of the function is (α,β]=(21,1]
⇒α=21,β=1
⇒α+β=23.
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