Paragraph: Read the following passage and answer the questions. For...

Paragraph: Read the following passage and answer the questions. For every function $f(x)$ which is twice differentiable, these will be good approximation of $\int_a^b f(x) d x \cong\left(\frac{b-a}{2}\right)\{f(a)+f(b)\}$. Now, if we take $c=\frac{a+b}{2}$, then using above again, we get $\int_a^b f(x) d x=\int_a^c f(x) d x+\int_c^b f(x) d x \cong \frac{b-a}{4}\{f(a)+f(b)+2 f(c)\}$ and so on. We get approximation for value of $\int_a^b f(x) d x$.Question: Good approximation of $\int_0^{\pi / 2} \sin x d x$, is