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Question: Answered & Verified by Expert
If $f(x)=a \cos (x+c)+d$, then range of $f(x)$ is
MathematicsFunctionsJEE Main
Options:
  • A $[d+a, d+2 a]$
  • B $[a-d, a+d]$
  • C $[d+a, a-d]$
  • D $[d-a, d+a]$
Solution:
2216 Upvotes Verified Answer
The correct answer is: $[d-a, d+a]$
$f(x)=a \cos (x+c)+d$ ....(i)
For minimum $\cos (x+c)=-1$
from (i), $f(x)=-a+d=(d-a)$
For maximum $\cos (x+c)=1$
from (i), $f(x)=a+d=(d+a)$

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