a(1−π2)a\left(1-\frac{\pi}{2}\right)a(1−2π)
a(1+π2)a\left(1+\frac{\pi}{2}\right)a(1+2π)
2π2\frac{2 \pi}{2}22π
a(π2−1)a\left(\frac{\pi}{2}-1\right)a(2π−1)