CBSE Class 11 » CBSE Class 11 Study Materials » Mathematics » Identifying Arithmetic progression

Identifying Arithmetic progression

A sequence, also known as a progression, is a list of numbers in a specific order. It is a string of numbers that follow a specific pattern, and all of the elements of a sequence are referred to as its terms. There are many different types of sequences that are universally accepted, but the one we'll be looking at right now is the arithmetic progression. An arithmetic progression, also known as an arithmetic sequence, is a series in which the difference between any two consecutive terms is constant. The difference between the consecutive terms is known as the common difference and is represented by the symbol d. An arithmetic progression (AP) is a sequence in which each term is found by adding a predetermined amount to the previous term. This fixed amount is referred to as the common difference.

An arithmetic progression (AP) is a sequence in which each term is found by adding a predetermined amount to the previous term. This fixed amount is referred to as the common difference. The difference between the consecutive terms is known as the common difference and is represented by the symbol d.

An arithmetic progression (AP) can be defined in two ways:

  • An arithmetic progression is a sequence in which the differences between each successive term are the same.
  • An arithmetic progression is a sequence in which each term, with the exception of the first, is obtained by adding a fixed number to the term before it.

For instance, 1, 5, 9, 13, 17, 21, 25, 29, 33,…

1 = a (the first term)

4 = d (the “common difference” between terms)

In general, an arithmetic sequence looks like this: a, a+d, a+2d, a+3d,…

Using the preceding example, we get: a, a+d, a+2d, a+3d,… = 1, 1+4, 1+24, 1+34,… = 1, 5, 9, 13,…

Arithmetic Progression is abbreviated as AP. To solve mathematical problems in an AP, three main terms are used:

  • Common distinction (d)
  • Term nth  (an)
  • Add the first n terms (Sn)

Sequences and series

One of the fundamental concepts in Arithmetic is the concept of sequence and series. Sequences are the ordered groupings of numbers that follow certain rules, whereas a series is the sum of the elements in the sequence. By solving problems based on the formulas, the fundamentals could be better understood. They are very similar to sets, but the main difference is that individual terms in a sequence can occur repeatedly in different positions. A sequence’s length is equal to the number of terms and can be finite or infinite.

Arithmetic progression

An arithmetic progression (AP) is a sequence in which the differences between each successive term are the same. It is possible to derive a formula for the nth term from an arithmetic progression. The sequence 2, 6, 10, 14, for example, is an arithmetic progression (AP) because it follows a pattern in which each number is obtained by adding 4 to its previous term. In this sequence, the nth term equals 4n-2. By substituting n =1, 2,3 in the nth term, the sequence’s terms can be obtained. i.e,

4n-2=4 when n=1.1-2=4-2=2

When n is equal to  2,4n-2=42-2=8-2=6

When n equals 3,4n-2 equals 4. (3)

-2=12-2=10

Arithmetic progression formula

The AP formulas are listed below.

  1. An AP’s most notable difference: d=a2-a1
  2.  nth term of an AP : an =a+n-1d
  3. The sum of an AP’s n terms is: Sn    =n/2(2a+n-1)d

Arithmetic Progressions’ (AP) Properties

  • If the same number is added or subtracted from each term of an A.P, the resulting terms in the sequence are also in A.P, but with the same common difference.
  • If every term in an A.P is divided or multiplied by the same non-zero number, the resulting sequence is also an A.P.
  • If 2y=x+z  three numbers x,y, and z are in an A.P.
  • If the nth the term of a sequence is a linear expression, the sequence is an A.P.
  • If we select terms from an A.P in a regular interval, these terms will also be in AP.

Arithmetic progression example

If l = 20, d = -1, and n = 17, then what is the first term?

Given: The final term of AP is referred to as l. Given l = 20, d = -1, and n = 17, we must locate a.

We can find a by using 

I=a+n-1d

a+17-1-1=20

a=20-16a=36

Conclusion

An arithmetic progression (AP) is a sequence in which each term is found by adding a predetermined amount to the previous term. This fixed amount is referred to as the common difference. The difference between the consecutive terms is known as the common difference and is represented by the symbol d. Arithmetic progression is a number sequence in which the difference between consecutive terms is constant. The arithmetic sequence can be used in almost every aspect of our lives. We simply need to consider how it can be applied in our daily lives. Knowing about this type of sequence can provide us with a new perspective on how things happen in our lives.

Types of Geometric progression

There are two kinds of geometric progression.

  • finite geometric progression 
  • Infinite geometric progression.

Finite geometric progression: There are only a finite number of terms in a finite geometric progression. It is in the progression that the final term is defined. For instance, 1/2,1/4,1/8,1/16,…,1/32768 is a finite geometric series with the last term being 1/32768.

Infinite geometric progression: There are an infinite number of terms in an infinite geometric progression. It is a progression in which the final term is not defined. For example, 3, 6, +12, 24, +… is an infinite series with no defined last term.

Geometric progression formula

To find the nth term in a progression, use the geometric progression formula. We need the first term and the common ratio to find the nth  term. If the common ratio is unknown, it is calculated by multiplying the ratio of any term by its preceding term. The formula for the geometric progression’s nth term is:

an=arn-1 

Where, The first term is a.

The common ratio is denoted by r.

n is the number of the term we’re looking for.

Sum of geometric progression

To find the sum of all the terms in a geometric progression, use the geometric progression sum formula. As we saw in the preceding section, geometric progression is classified into two types: finite and infinite geometric progressions, and the sum of their terms is calculated using different formulas.

 Finite Geometric Series:

If the number of terms in a geometric progression is finite, the sum of the geometric series is calculated using the following formula:

Sn  =a1-rn1-rfor r≠1

Sn=an for r=1 

Where, The first term is ” a”.

The common ratio is denoted by  r.

n Denotes the number of terms in the series.

Infinite Geometric Series:

An infinite geometric series sum formula is used when the number of terms in a geometric progression is infinite. There are two cases in an infinite series, depending on the value of r. Let’s look at the infinite series sum formula for both cases.

In Case 1: When |r| is greater than one r<1

S∞  =a/(1-r) 

Where, The first term is a.

The common ratio is denoted by r.

In Case 2: When r is greater than one r>1

The series does not converge (i.e., it diverges) in this case, and it has no sum.

Geometric progression example

Check to see if the given sequence, 9, 3, 1, 1/3, 1/9……, is in geometrical progression.

Solution: Calculate the ratio of the consecutive terms, a1 = 9 and a2 = 3. So,

a2a1 = 39 =13

= a3a2 = 13

Because the ratio of the given sequence’s consecutive terms is 13 a fixed number, this sequence is in geometrical progression.

Conclusion

Geometric progressions can have finite or infinite lengths. Its common ratio can be either negative or positive. In this section, we will learn more about the GP formulas and the various types of geometric progressions. A geometric progression, also known as a geometric sequence, is a non-zero number sequence in which each term after the first is found by multiplying the previous one by a fixed, non-zero number known as the common ratio.

faq

Frequently asked questions

Get answers to the most common queries related to the CBSE Class 11 Examination Preparation.

Do we need a unit circle method for finding the values of trigonometric functions for angles less than 90 degrees?

Ans: No. The unit circle method is applicable for finding the values of trigonometric functions for angles more than...Read full

Do we need to memorize the unit circle diagram for finding the values of trigonometric functions?

Ans. Yes. It would be better to memorize the unit circle diagram for finding the values of trigonometric functions a...Read full

Can we directly use the unit circle diagram to find the values of trigonometric functions concerning tangent?

Ans: No. The values of trigonometric functions displayed in the unit circle diagram only concern the sine and cosine...Read full

Is quadrant an essential component for finding the values of trigonometric functions?

Ans: Absolutely. To find the values of trigonometric functions, it is imperative to find which quadrant the angle of...Read full