RD Sharma Solutions Class 11 Sine And Cosine Formulae And Their Applications

RD Sharma Solutions Class 11 Chapter 10

Trigonometry, a branch of Mathematics which deals with the triangles and is also known as the study of relationships between angles and lengths of triangles. There are several of uses of trigonometry and its formula.

For example, It is used in geography for measuring the distance between the landmarks and in astronomy for measuring the distance between nearby stars and also in satellite navigation systems.

In Trigonometry, the law of sines is also known as Sine Formula or Sine Rule and cosines is also known as Cosine Rule or Cosine Formula.

These rules are related to the lengths, sides, and angles of a triangle.

The Sine Rule

sin A / a = sin B / b = sin C / c = 1 / 2R.

Here R is the radius of the circumstance of the triangle ABC.

The sine rule is used to predict unknown values for two congruent triangles.

The Cosine Rule

\(a^{2}=b^{2}+c^{2}-2bc\cos A\)

\(b^{2}=a^{2}+c^{2}-2ac\cos B\)

\(c^{2}=a^{2}+b^{2}-2ab\cos C\)

The cosine rule is used to predict the third side of a triangle when other sides and the angle are given.

Practice problems on Sine and Cosine rules through solved RD Sharma solutions to have a better understanding of the topic.

Practise This Question

The points A(-a,b), B(-a,c) and C(a,c) form the vertices of a triangle. Which of the following is true?