The value of $\int\limits_{0}^{\frac{\pi}{4}} (\sin 2x) dx$ is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → $\frac{1}{2}$
$\int\limits_{0}^{\frac{\pi}{4}} (\sin 2x) dx = \int\limits_{0}^{\frac{\pi}{4}} 2 \sin x \cos x \, dx$
Let $\sin x = t$
$\cos x \, dx = dt$
When $x = 0$ then $t = 0$
When $x = \frac{\pi}{4}$ then $t = \frac{1}{\sqrt{2}}$
$= 2 \int\limits_{0}^{\frac{1}{\sqrt{2}}} t \, dt$
$= 2 \left[ \frac{t^2}{2} \right]_{0}^{\frac{1}{\sqrt{2}}}$
$= \frac{1}{2} - 0 = \frac{1}{2}$