- 1. CIRCLES PRESENTED BY ADAMYA SHYAM
- 2. CIRCLE DEFINITION A Circle is a simple shape of Euclidean geometry that is the set of points in the plane that are equidistant from a given point, the centre. The distance between any of the points on the circle and the centre is called the radius. A circle is a simple closed curve which divides the plane into 3 regions: Interior, Exterior and On The Circle . In everyday use, the term "circle" may be used interchangeably to refer to either the boundary of the figure, or to the whole figure including its interior; in strict technical usage, the circle is the former and the latter is called a disk. A circle can be defined as the curve traced out by a point that moves so that its distance from a given point is constant. A circle may also be defined as a special ellipse in which the two foci are coincident and the eccentricity is 0. Circles are conic sections attained when a right circular cone is intersected by a plane perpendicular to the axis of the cone.
- 3. CIRCLE HISTORY The word "circle" derives from the Greek, kirkos "a circle," from the base Ker- which means to turn or bend. The origins of the words "circus" and "circuit" are closely related. The circle has been known since before the beginning of recorded history. Natural circles would have been observed, such as the Moon, Sun, and a short plant stalk blowing in the wind on sand, which forms a circle shape in the sand. The circle is the basis for the wheel, which, with related inventions such as gears, makes much of modern civilization possible. In mathematics, the study of the circle has helped inspire the development of geometry, astronomy, and calculus. Early science, particularly geometry and astrology and astronomy was connected to the divine for most medieval scholars, and many believed that there was something intrinsically "divine" or "perfect" that could be found in circles.
- 4. CIRCLE TERMINOLOGY Chord: A line segment whose endpoints lie on the circle. Diameter: A line segment whose endpoints lie on the Circle and which passes through the centre. Radius: Half of Diameter Arc: Any connected part of the circle's circumference. Sector: A region bounded by two radii and an arc lying between the radii. Segment: A region bounded by a chord and an arc lying between the chord's endpoints.
- 5. CIRCLE CHORD Chords are equidistant from the centre of a circle if and only if they are equal in length. If a central angle and an inscribed angle of a circle are subtended by the same chord and on the same side of the chord, then the central angle is twice the inscribed angle. If two angles are inscribed on the same chord and on the same side of the chord, then they are equal. If two angles are inscribed on the same chord and on opposite sides of the chord, then they are supplemental. An inscribed angle subtended by a diameter is a right angle. The diameter is the longest chord of the circle. If the intersection of any two perpendicular chords divides one chord into lengths a and b and divides the other chord into lengths c and d, then a2 + b2 + c2 + d2 equals the square of the diameter. The distance from a point on the circle to a given chord times the diameter of the circle equals the product of the distances from the point to the ends of the chord.
- 6. CIRCLE DIAMETER In geometry, the diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the boundary of the circle. The diameters are the longest chords of the circle. In this sense one speaks of diameter rather than a diameter, because all diameters of a circle have the same length, this being twice the radius. For a convex shape in the plane, the diameter is defined to be the largest distance that can be formed between two opposite parallel lines tangent to its boundary, and the width is defined to be the smallest such distance. For a curve of constant width such as the Reuleaux triangle, the width and diameter are the same because all such pairs of parallel tangent lines have the same distance. See also Tangent lines to circles.
- 7. CIRCLE RADIUS In classical geometry, a radius of a circle is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its circum radius, the radius of its circumscribed circle . In either case, the radius may be more than half the diameter, which is usually defined as the maximum distance between any two points of the figure. The in radius of a geometric figure is usually the radius of the largest circle or sphere contained in it. The inner radius of a ring, tube or other hollow object is the radius of its cavity. For regular polygons, the radius is the same as its circumradius.The name comes from Latin radius, meaning "ray" but also the spoke of a chariot wheel.
- 8. CIRCLE ARC & SECTOR In geometry, an arc is a closed segment of a differentiable curve in the two-dimensional plane; for example, a circular arc is a segment of the circumference of a circle. If the arc is part of a great circle , it is called a great arc. A circular sector or circle sector, is the portion of a disk enclosed by two radii and an arc, where the smaller area is known as the minor sector and the larger being the major sector. In the diagram, θ is the central angle in radians, the radius of the circle, and is the arc length of the minor sector. A sector with the central angle of 180° is called a semicircle. Sectors with other central angles are sometimes given special names, these include quadrants (90°), sextants (60°) and octants (45°).
- 9. CIRCLE SEGMENT In geometry, a circular segment is an area of a circle informally defined as an area which is "cut off" from the rest of the circle by a chord. The circle segment constitutes the part between the secant and an arc, excluding of the circle's center. SEGMENT CHORD RADIUS CENTRE DIAMETER SECTOR
- 10. CIRCLE THEOREMS The chord theorem states that if two chords, CD and EB, intersect at A, then CA × DA = EA × BA. If a tangent from an external point D meets the circle at C and a secant from the external point D meets the circle at G and E respectively, then DC2 = DG × DE. If two secants, DG and DE, also cut the circle at H and F respectively, then DH × DG = DF × DE. The angle between a tangent and chord is equal to one half the subtended angle on the opposite side of the chord. If the angle subtended by the chord at the centre is 90 degrees then l = r√2, where l is the length of the chord and r is the radius of the circle. If two secants are inscribed in the circle as shown at right, then the measurement of angle A is equal to one half the difference of the measurements of the enclosed arcs.