+) Ta có: S=\pi r^{2}=\pi.\dfrac{d^{2}}{4}=\pi \dfrac{50,6^{2}}{4}\approx 2010,9mm^{2}
+) S_{min}=\pi r'^{2}=\pi.\dfrac{d'^{2}}{4}=\pi \dfrac{50,5^{2}}{4}\approx 2003,0mm^{2}
+) S_{max}=\pi r'^{2}=\pi.\dfrac{d'^{2}}{4}=\pi \dfrac{50,7^{2}}{4}\approx 2018,9mm^{2}
+) \Delta...