**ICOSAEDRO - **A polyhedron with 20 faces.

**IDENTITY -** Way of showing that two expressions have the same value.

**Odd - **It is said of the integer that is not divisible by 2 or what has no 2 as a factor.

**SLOPE OF A STRAIGHT **If two points on a line have the same abscissa, the line is said to be vertical and if the abscissa is different the line is inclined. When possible, the inclination is obtained by dividing the difference between the ordinates and the difference of the abscissae of any two points.

**INDEX - **The value at the root of a number indicating the exponent by which the result must be raised to obtain that number.

**INQUIRY - **Inequality verified at certain value (s) assigned to the variable.

**INFINITE **- That is not finite. The set of natural numbers is infinite, because there will always be another natural that surpasses the previous one. It means something so big that it can't be counted.

**INTEGRAL - **Inverse function of the derivative. Function that generates, from how the variables of a given function relate, another broader function, which describes a broader behavior (integral).

**INTERPOLATION - **Method for finding succession values between two known consecutive values.

**INTERSECTION** - The intersection of two sets is the set of all elements that belong to the two sets simultaneously. The intersection of sets A and B is denoted by A_{}B and read "Intersection B". The intersection of sets satisfies the following properties:

- THE
_{}A = A and A_{}=_{} - THE
_{}B = B_{}A (Intersection is commutative) - (THE
_{}B)_{}C = A_{}(B_{}C) (Intersection is associative).

**INTERVAL - **A finite range of the real line _{} is a subset of _{} which has one of the following forms:

- a, b = {x real: a <× <b}
- (a, b) = {x actual: a <× <b}
- a, b) = {x real: a <× <b}
- (a, b = {x actual: a <× <b}

**INVERSE** - Contrary, inverted, opposite.

**SWEAR** - Profit calculated on a given rate of borrowed money or capital employed; income, interest.

**SIMPLE INTEREST** - The interest of each time interval is always calculated on the initial borrowed or invested capital.

**COMPOUND INTEREST **- The interest of each time interval is calculated from the balance at the beginning of the corresponding interval. That is, the interest of each time interval is incorporated into the initial capital and yields interest as well.

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