If $f(x)=a\cos (bx+c)+d$, then what is the range of f(x)?

[d – a, a] [d – a, d + a] [d – a, –d + a] [a – d, a + d]

[d – a, d + a]

$f(x)=a\cos (bx+c)+d$   . . . .(i) For minimum $\cos (bx+c)=-1$ From (i), $f(x)=-a+d=(d-a)$ For maximum $\cos (bx+c)=1$ From (i), $f(x)=a+d=(d+a)$ Range of $f(x)=[d-a,d+a]$