1.

The set of all real values of x for which the funciton `f(x) = sqrt(sin x + cos x )+sqrt(7x -x^(2) - 6)` takes real values isA. `[1, 3pi//4] uu [7pi//4, 6]`B. `[1, 3pi//4]uu [ 6- pi//4, 6]`C. `[1, 6]`D. none of these

Answer» Correct Answer - A
We have,
`f(x) = sqrt(sin x + cos x) + sqrt(7x- x^(2) - 6)`
`rArr (x) = 2^(1//4) sqrt(sin (x+ pi//4)) + sqrt(7x-x^(2)-6)`
For f(x) to be real, we must have
`sin (x+(pi)/(4)) gt 0 and 7x - x^(2) - 6 gt 0`
`rArr 2npi le x +(pi)/(4) le (2n+1) pi and 1 le x le 6`, where `n in Z`
`rArr x in [1,(3pi)/(4)]uu[(7x)/(4) ,6]`


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