What is the area bounded by $y = \cos x$, the $x$-axis and the lines $x = \frac{\pi}{2}$ and $x = \pi$?

Explanation

1. 01

   On $[\frac{\pi}{2}, \pi]$ the curve lies below the $x$-axis, so the integral comes out negative: $-1$.

2. 02

   An area is never negative: it is $\left|-1\right| = 1$ square units.