Spherical sector

The spherical sector has axial section has an angle of α = 120° in the center of the sphere, is part of a sphere with a radius r = 10 cm. Calculate the surface of this spherical sector.

Final Answer:

S =  586.2292 cm²

Step-by-step explanation:

$$\begin{gathered} \alpha =120{}^{\circ } \\ r=10\text{cm} \\ \sin \alpha /2=a:r \\ a=r\cdot \sin (\alpha /2)=10\cdot \sin (120°/2)=8.66025\text{cm} \\ h=r-\sqrt{r^2-a^2}=10-\sqrt{10^2-8.6603^2}=5\text{cm} \\ {S}_1=2\pi \cdot r\cdot h=2\cdot 3.1416\cdot 10\cdot 5\doteq 314.1593{\text{cm}}^2 \\ {S}_2=\pi \cdot a\cdot r=3.1416\cdot 8.6603\cdot 10\doteq 272.0699{\text{cm}}^2 \\ S=S_1+S_2=314.1593+272.0699=586.2292{\text{cm}}^2 \end{gathered}$$

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