=2(π4−24)=2\left(\frac{\pi}{4}-\frac{2}{4}\right)=2(4π−42)
=2(π4−23)=2\left(\frac{\pi}{4}-\frac{2}{3}\right)=2(4π−32)
=2(π4+23)=2\left(\frac{\pi}{4}+\frac{2}{3}\right)=2(4π+32)
=−2(π4−23)=- 2\left(\frac{\pi}{4}-\frac{2}{3}\right)=−2(4π−32)