ISI2017-DCG-25

Question

If $f(x) = \begin{vmatrix} 2 \cos ^2 x & \sin 2x & – \sin x \\ \sin 2x & 2 \sin ^2 x & \cos x \\ \sin x & – \cos x & 0 \end{vmatrix},$  then $\int_0^{\frac{\pi}{2}} [ f(x) + f’(x)] dx$  is

• A. $\pi$
• B. $\frac{\pi}{2}$
• C. $0$
• D. $1$

Comments

Just solving determinant will give the answer in this question.

Answer 1

after solving determinant $\Delta = 2$

so $\int_{0}^{\pi/2} 2 \ dx = \pi$

Answer is A.

Comments

correct