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"If a sector revolves about its bounding radius as an axis, it generates what may be called a spherical cone."

Spherical Cone

"If a sector revolves about its bounding radius as an axis, it generates what may be called a spherical…

Diagram used to prove the theorem: "The area of the surface generated by a straight line revolving about an axis in its plane is equal to the product of the projection of the line on the axis by the circumference whose radius is perpendicular erected at the middle point of the line and terminated by the axis."

Area of Surface Generated by a Straight Line

Diagram used to prove the theorem: "The area of the surface generated by a straight line revolving about…