Mathematics is the base of human civilization. From cutting vegetables to arranging books on the shelves, from tailoring clothes to motion of Planets - Mathematics applies everywhere.

Number System | Calculus | Probability | Trigonometry | Geometry & Mensuration | Algebra & Arithmetic | Coordinate Geometry

**(a)** Consider the addition of rational numbers with same denominators: p/q and r/q

When an **integer a is divided by another non-zero integer b**. The following cases arise:

While dealing with natural numbers and whole numbers, it is not always possible to subtract a number from another. For example, (2 – 3), (3 – 7), and (9 – 20) are all not possible in the system of natural numbers and whole numbers. Thus, it needed another extension of numbers which allow such subtractions.

The **counting numbers 1, 2, 3, ...** constitute the system of natural numbers. These are the numbers which are used in day-to-day life.

The term ‘Geometry’ is the English equivalent of the Greek word ‘**Geometron**’. ‘Geo’ means Earth and ‘metron’ means Measurement. According to historians, the geometrical ideas shaped up in ancient times, probably due to the need in art, architecture and measurement. These include occasions when the boundaries of cultivated lands had to be marked without giving room for complaints.

When a number is expressed as a product of its factors, the number is said to be **factorised**.

You can find a pattern that can tell whether a number is divisible by 2, 3, 4, 5, 6, 8, 9, 10 or 11.

In the numbers 2, 4, 6, 8, 10, 12, 14, ... each of them is a multiple of 2. These are called even numbers.

There are numbers, having exactly two factors 1 and the number itself. Such number are 2, 3, 5, 7, 11, and so on. These numbers are prime numbers.

You can find the **common factors** of any two numbers. For example, the common factors of 12 and 16 are 1, 2 and 4. The highest of these common factors is 4.

The Lowest Common Multiple (LCM) of two or more given numbers is the lowest (or smallest or least) of their common multiples. For example, the common multiples of 4 and 6 are 12, 24, 36, ... . The lowest of these is 12. So, the lowest common multiple of 4 and 6 is 12.

A factor of a number is an **exact divisor** of that number. For example, 1, 2, 3 and 6 are exact divisors of 6. They are called the factors of 6.

Given any natural number, you can add 1 to that number and get the next number i.e. you get its **successor**. The successor of 16 is 16 + 1 = 17, that of 19 is 19 +1 = 20 and so on. The number 16 comes before 17, we say that the **predecessor** of 17 is 17 – 1 = 16, the predecessor of 20 is 20 – 1 = 19, and so on. Does 1 have both a successor and a predecessor?

A is called the arithmetic mean of the numbers a and b if and only if a, A, b are in AP.

A sequence of non-zero numbers is said to be in harmonic progression (HP) if their reciprocals are in AP.

A geometric progression (GP) is a sequence of numbers in which the first term is non-zero and each term, except the first, is obtained by multiplying the term immediately preceding it by a fixed non-zero number. This fixed number is called the **common ratio** and it is denoted by r.

An arithmetic progression (AP) is a sequence of numbers in which each term, except the first, is obtained by adding a fixed number to the immediately preceding term. This fixed number is called the **common difference**, which is generally denoted by d.

A **Binomial** is an algebraic expression of two terms which are connected by the operation: + or −.

**Induction** is the process of inferring a general statement from the truth of particular cases.

The word combination means **selection**. Suppose you are asked to make a selection of any two things from three things: a, b and c.

A circular permutation is one in which the things are arranged along a circle. It is also called **closed permutation**.

The number of permutations of n different things, taken r at a time, when each may be repeated any number of times in each arrangement, is **n ^{r}**.

The number of mutually distinguishable permutations of n things, taken all at a time, of which p are alike of one kind, q alike of second such that p + q = n, is **n!/p! q!**.

The scalar product of two vectors is a scalar quantity. Therefore, the product is called scalar product.

Any three numbers proportional to direction cosines of a vector are called its direction ratios.

Let P(x, y, z) be any point in space with reference to a rectangular coordinate system O (XYZ). Let α, β and γ be the angles made by OP with the positive direction of coordinate axes OX, OY, OZ respectively. Then cos α, cos β, cos γ are called the direction cosines.

If P is a point in a two dimensional plane which has coordinates (x, y).

Triangle Law of Addition of vectors states that, if two vectors are represented in magnitude and direction by the two sides of a triangle taken in the same order, then their sum is represented by the third side taken in the reverse order.

A vector whose initial and terminal points are coincident is called a zero or null or a void vector. The zero vector is denoted by .

Physical quantities are divided into two categories: Scalar quantities and Vector quantities.

The quantities sin^{−1}x, cos^{−1}x, tan^{−1}x are called inverse circular functions. sin^{−1}x is an angle θ, whose sine is x.

A triangle has six parts or elements - the sides a, b, c and the angles A, B, C.

**θ = nπ + (−1) ^{n}α**, where n ∈ Z

a cosθ + b sinθ = c where c^{2} ≤ a^{2} + b^{2}

Divide each term by √(a^{2} + b^{2})

The general solution of sin θ = 0 is given by

**θ = nπ**, n ∈ Z where Z is the set of all integers.

An equation involving trigonometrical function is called a trigonometrical equation. To solve these equations, you are required to find all replacements for the variable θ that make the equations true.

Identities involving sin 2A, cos 2A, tan 3A, etc. are called multiple angle identities. To derive these identities you can use sum identities.

The relation f(x+ y) = f(x) + f(y) is not true for all functions of a real variable. All the six trigonometric ratios do not satisfy this relation.

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