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A Glossary of Mathematical Terms - I

Icosahedron

A 20-sided solid;, each face is in the shape of a triangle.

Identity element

In operations (addition, multiplication, ...) the element that is neitral as far as the outcome is concerned.

If and only if.

Imaginary number

A complex number with no real part.

See fraction.

Improper subset

The null subset of a set or the whole set as a subset.

Integer

A member of the set {0, +1, -1, +2, -2, ... }.

Intercept

The point where a curve meets the x-axis (x-intercept) or the y-axis (y-intercept).

Interior angles

Usually referred to the angles of a polygon.

Intersection of sets

The set consisting of all elements that are common to two or more sets.

Interval

The set of all real (rational) numbers betwenn two fixed real (rational) numbers.

Isometry

A tarnsformation that keeps the same size and shape of figures.

Isosceles

A polygon with two sides equal in length. Usually referred to triangles and trapezoids.

first published on september 01 2003 - last updated on september 01 2003