# Math Dictionary p

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**Parabola:**Any plane section of a circular conical surface by a plane parallel to the slant height of the cone.

**Paragraph proof:**A written proof in which the statements and their corresponding reasons are written, in paragraph form, using complete sentences.

**Parallelepiped:**A prism whose bases are parallelograms.

**Parallel lines:**Two or more coplanar lines that do not intersect. Parallel line segments or rays are line segments or rays that are subsets of parallel lines.

**Parallel planes:**Two or more planes that do not intersect.

**Parallel postulate:**Any postulate or axiom that designates the number of lines through a given point that are parallel to a given line.

**Parallelogram:**A quadrilateral in which both pairs of opposite sides are parallel.

**Parameter:**A quantity or constant whose value varies with the circumstances of its application.

**Pentagon**A polygon with 5 sides.

**Percent :**Percent means parts per 100.The symbol is %.

**Perfect Square :**A number made by squaring a whole number.

**Perimeter:**The sum of the lengths of all the sides of any polygon.

**Permutation :**All possible arrangements of a collection of things.

**Perpendicular bisector:**A line, segment or ray that is perpendicular to a line segment at its midpoint.

**Perpendicular lines:**Two lines that intersect to form right angles.

**Perpendicular planes:**Two planes that intersect to form right dihedral angles.

**Pi:**The irrational number equal to the length of the circumference of a circle divided by the length of its diameter.

**Plane:**An undefined term in geometry usually visualized as a flat surface with no thickness that extends indefinitely in two dimensions.

**Platonic solids:**The five regular polyhedra: tetrahedron, cube, octahedron, dodecahedron and icosahedron.

**PM :**Is the half of the day from Midday to Midnight.What we call afternoon and evening.It comes from the Latin "Post Meridiem" for "after midday".

**Point:**An undefined term in geometry usually visualized as a dot representing a nondimensional location in space.

**Point of concurrency:**A point that is the intersection of three or more lines.

**Point of tangency:**The point where a tangent line intersects a curve.

**Point-slope equation of a line:**The equation of a line formed using its slope and the coordinates of a point on the line, where m is the slope of the line and (x1, y1) are the coordinates of the given point.

**Point symmetry:**A geometric figure has point symmetry if every point on the figure is the image of itself under a rotation of 180° about some fixed point.A regular hexagon has point A pentagon does not have symmetry about its center. point symmetry

**Polygon:**A closed plane figure formed by three or more line segments that meet only at their endpoints.

**Polyhedron:**A solid figure bounded by polygons.

**Position vector:**A coordinate vector whose initial point is the origin. Any vector can be expressed as an equivalent position vector by translating the vector so that it originates at the origin.

**Postulate:**A statement assumed to be true without proof.

**Power Set :**"The set of all the subsets of a set".

**Preimage:**The original point or points of a transformation.

**Premise:**A proposition upon which an argument is based or from which a conclusion is drawn.

**Prime Number :**A Prime Number can be divided evenly only by 1 or itself.And it must be greater than 1.

**Prism:**A polyhedron with two congruent, parallel, polygonal bases and whose lateral faces are parallelograms.

**Probability :**Probability is the chance that something will happen - how likely it is that some event will happen.(from math dictionary p)

**Proof by contradiction:**A method of proof which demonstrates the truth of an implication by proving that the negation of the conclusion of that implication leads to a contradiction; also called an indirect proof.

**Proper Fraction :**A proper fraction is a fraction where the numerator (the top number) is less than the denominator (the bottom number).

**Proportional:**Two variables are proportional if they maintain a constant ratio. See also direct variation.

**Pyramid:**A polyhedron having a polygonal base and triangles as lateral faces.

**Pythagorean theorem:**The mathematical relationship stating that in any right triangle the sum of the squares of the lengths of the two legs is equal to the square of the length of the hypotenuse; if a and b are the lengths of the legs and c is the length of the hypotenuse, then a

^{2}+ b

^{2}= c

^{2}. (from math dictionary p)

**Math dictionary p**

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