MATH DICTIONARY

I

i:  the basic unit for the imaginary number:   i2 = -1.

icosohedron:  a polyhedron with 20 faces.

identity: an equation that is true for all values of the variable.

identity element:   If * is an operator, then the identity element, I, for * is the number such

that I * a = a.   The identity for addition is zero, and the identity for

multiplication is 1.

identity matrix:    a square matrix with ones along the diagonal and zeros everywhere else.

If I is an identity matrix, then IA = A.

imaginary number:   a number of the form ni, where n is a real number, and i2 = -1.

implication:   a conditional statement.

improper fraction:  a fraction with a numerator that is greater than the denominator.

incenter:  the center of a circle that is inscribed in a triangle.   The intersection of the

angle bisectors of the triangle.

incircle:   the circle that can be inscribed in a triangle.

increasing function:  a function is increasing if f(a) > f(b) when a > b.

increment:  a small change, usually indicated by the greek letter delta.

indefinite integral:  the sum of the antiderivative of a function and an arbitrary constant.

independent variable:  the input number to a function.

infinity:  a limitless quantity.

inflection point:  a point on a curve such that the curve is concave up on one side of the

point, and concave down on the other side of the point.

inscribed polygon:  a polygon placed inside a circle so that each vertex of the polygon

touches the circle.

integers:  the set of numbers containing zero, the natural numbers, and all the negatives of
the natural numbers.

integral:   If  dF(x)/dx = f(x), then F(x) is an integral of f(x).   The area under the curve of a

function above the x - axis.

integrand:  a function that is to be integrated.

integration:  the process of finding an integral.

intercept:  the x-intercept of a curve is the point where the curve crosses the x - axis, and

the y - intercept of a curve is the point where the curve crosses the y - axis.

inversely proportional:   y is inversely proportional to x if y = k/x.

irrational number:  a number that cannot be expressed as the ratio of two integers.

isometry:  a transformation of a figure that does not change the distances of any two

points in the figure.

isosceles triangle:  a triangle with at least two equal sides.

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