Question:

The value of \[ \int (\log\sec x)\tan x\,dx \] is

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Use substitution when one factor is the derivative of another factor.
  • \(\sec x+c\)
  • \(\log\sec x+c\)
  • \(\frac{1}{2}(\log\sec x)^2+c\)
  • \(\log(\log\sec x)\)
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The Correct Option is C

Solution and Explanation


Step 1:
Let: \[ t=\log\sec x \]

Step 2:
Differentiate: \[ dt=\tan x\,dx \]

Step 3:
Therefore: \[ \int(\log\sec x)\tan x\,dx = \int t\,dt \]

Step 4:
\[ \int t\,dt=\frac{t^2}{2}+c \]

Step 5:
Substitute \(t=\log\sec x\): \[ \frac{1}{2}(\log\sec x)^2+c \] \[ \boxed{\frac{1}{2}(\log\sec x)^2+c} \]
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