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# RS Aggarwal Class 11 Chapter 18 Solutions (Solution of Triangles)

RS Aggarwal Class 11 Chapter 18 is one of the trusted books that help you build a strong foundation for CBSE class 11th and class 12th. This book has questions according to the latest exam patterns of CBSE, IIT, JEE, etc. If you are one of those who are preparing for the competitive exams, then each and every question of the book is going to be helpful for you.

Chapter 18 Solution of triangles has only two exercises with around 25 questions. The questions range from the basic level to the advanced level. The exercise will help you in preparing well for your final exams as the exercises have a variety of questions. In the chapter, you will learn about different topics like an oblique triangle, sine formula, cosine rule, Napier’s analogies, etc.

RS Aggarwal Class 11 Maths Solutions of Triangles by Instasolv provides you with the best solutions to all the questions. The questions range from simple to difficult levels but the Instasolv team will make the course content and the other concepts easy for you in several ways. All you need is to get in touch with our experts and make your maths study easy.

### Topics Covered under Chapter 18

Parts of a Triangle

The three sides, as well as three angles of a triangle, are known as the parts of the triangle.

Solving the Triangle

Solving a figure requires different processes. The process of computing the measures of all the unknown parts of a triangle from those of the given parts refers to solving the triangle.

Oblique Triangle

A triangle with no re=ight angle is known as an oblique triangle.

Theorem 1

This theorem is also known as sine rule or sine formula. In any triangle, the sides of the triangle are proportional to the sines of the opposite angles.

In a triangle ABC,

Theorem 2

This theorem is also known as cosine formula. If a, b, and c are the length of sides of triangle ABC, opposite to ∠A, ∠B, and ∠C, respectively. Then,

• a2 = b2 + c2 – 2bc cos A
• b2 = c2 + a2 – 2ca cos B
• c2 = a2 + b2 – 2ab cos C

Napier’s Analogies

In any triangle ABC,

• tan (B – C)/2 = (b – c)/(b +c) cot A/2
• tan (C – A)/2 = (c –a)/(c + a) cot B/2
• tan (A – B)/2 = (a – b) /(a + b) cot c/2

Projection Rule

• a = b cos C + c cos B
• b = c cos A + a cos C
• c = a cos B + b cos A

If you have any three elements of a triangle like two sides and an angle then you can easily find out the rest elements using several formulae listed above. Hence, you can know the triangle completely and can find the solution of a triangle.

Exercise Wise Discussion of RS Aggarwal Chapter 18

• The chapter has two exercises with only 25 questions.
• The first exercise 18A has 22 questions in which you need to solve the triangle in different ways.
• The second exercise has only 3 questions in which you have to find the distance in different situations.

## Benefits of RS Aggarwal Class 11 Chapter 18 Solutions of a Triangle by Instasolv

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