Integral Calculus Question 410

Question: $ \int_{{}}^{{}}{\tan (3x-5)\sec (3x-5)\ dx=} $

[MP PET 1988]

Options:

A) $ \sec (3x-5)+c $

B) $ \frac{1}{3}\sec (3x-5)+c $

C) $ \tan (3x-5)+c $

D) None of these

Show Answer

Answer:

Correct Answer: B

Solution:

Put $ t=3x-5\Rightarrow dt=3dx, $ therefore $ \int_{{}}^{{}}{\tan (3x-5),\sec (3x-5),dx}=\frac{1}{3}\int_{{}}^{{}}{\tan t.\sec t,dt} $ $ =\frac{\sec t}{3}+c=\frac{\sec (3x-5)}{3}+c. $