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  2. Torus - Wikipedia

    en.wikipedia.org/wiki/Torus

    These formulas are the same as for a cylinder of length 2πR and radius r, obtained from cutting the tube along the plane of a small circle, and unrolling it by straightening out (rectifying) the line running around the center of the tube. The losses in surface area and volume on the inner side of the tube exactly cancel out the gains on the ...

  3. Right circular cylinder - Wikipedia

    en.wikipedia.org/wiki/Right_circular_cylinder

    The area of the base of a cylinder is the area of a circle (in this case we define that the circle has a radius with measure ): B = π r 2 {\displaystyle B=\pi r^{2}} . To calculate the total area of a right circular cylinder, you simply add the lateral area to the area of the two bases:

  4. Surface of revolution - Wikipedia

    en.wikipedia.org/wiki/Surface_of_revolution

    A portion of the curve x = 2 + cos(z) rotated around the z-axis A torus as a square revolved around an axis parallel to one of its diagonals.. A surface of revolution is a surface in Euclidean space created by rotating a curve (the generatrix) one full revolution around an axis of rotation (normally not intersecting the generatrix, except at its endpoints). [1]

  5. Solid of revolution - Wikipedia

    en.wikipedia.org/wiki/Solid_of_revolution

    Two common methods for finding the volume of a solid of revolution are the disc method and the shell method of integration.To apply these methods, it is easiest to draw the graph in question; identify the area that is to be revolved about the axis of revolution; determine the volume of either a disc-shaped slice of the solid, with thickness δx, or a cylindrical shell of width δx; and then ...

  6. Straightedge and compass construction - Wikipedia

    en.wikipedia.org/wiki/Straightedge_and_compass...

    Creating the line through two points; Creating the circle that contains one point and has a center at another point; Creating the point at the intersection of two (non-parallel) lines; Creating the one point or two points in the intersection of a line and a circle (if they intersect)

  7. Bicentric quadrilateral - Wikipedia

    en.wikipedia.org/wiki/Bicentric_quadrilateral

    If M, N are the midpoints of the diagonals, and E, F are the intersection points of the extensions of opposite sides, then the area can also be expressed as = ¯ ¯ ¯ where Q is the foot of the perpendicular to the line EF through the center of the incircle. [9]

  8. Area of a circle - Wikipedia

    en.wikipedia.org/wiki/Area_of_a_circle

    The area of a regular polygon is half its perimeter multiplied by the distance from its center to its sides, and because the sequence tends to a circle, the corresponding formula–that the area is half the circumference times the radius–namely, A = ⁠ 1 / 2 ⁠ × 2πr × r, holds for a circle.

  9. Napkin ring problem - Wikipedia

    en.wikipedia.org/wiki/Napkin_ring_problem

    The cross-section's area is therefore the area of the larger circle minus the area of the smaller circle: () = (()) = (()). The radius R does not appear in the last quantity. Therefore, the area of the horizontal cross-section at height y {\displaystyle y} does not depend on R {\displaystyle R} , as long as y ≤ h 2 ≤ R {\displaystyle y\leq ...