Class 10 Maths (Ganit) Chapter 8 PDF: त्रिकोणमिति का परिचय (Introduction to Trigonometry)

Class 10 Maths Chapter 8, Introduction to Trigonometry, defines the six trigonometric ratios of an acute angle in a right triangle, derives the exact values of trigonometric ratios at 0°, 30°, 45°, 60° and 90°, and proves the three fundamental Pythagorean trigonometric identities.

What Class 10 Mathematics (Ganit — Hindi Medium) Chapter 8 Covers

8.1 & 8.2 Trigonometric Ratios defines sin A = Opposite/Hypotenuse, cos A = Adjacent/Hypotenuse, tan A = Opposite/Adjacent = sin A / cos A, and their reciprocals csc A, sec A and cot A, showing that these ratios depend only on the angle A and not on the size of the right triangle.

8.3 Trigonometric Ratios of Some Specific Angles uses an isosceles right triangle (45°) and an equilateral triangle (30° and 60°), along with limiting behaviour at 0° and 90°, to build the complete standard table of trigonometric values.

8.4 Trigonometric Identities proves from Pythagoras’s theorem that sin² A + cos² A = 1, 1 + tan² A = sec² A (0° ≤ A < 90°), and cot² A + 1 = csc² A (0° < A ≤ 90°).

Exercises in Chapter 8

• Exercise 8.1 (11 Questions) computes all trigonometric ratios given one ratio or two sides of a right triangle using Pythagoras’s theorem.
• Exercise 8.2 (4 Questions) evaluates expressions using trigonometric values at 0°, 30°, 45°, 60° and 90°, and solves equations like tan (A + B) = √3, tan (A – B) = 1/√3.
• Exercise 8.3 (4 Questions, including the 10-part identity proof question) practices expressing all ratios in terms of sec A and proving classic trigonometric identities.

Read Class 10 Mathematics (Ganit — Hindi Medium) Chapter 8 Online

More Chapters

• Previous: Chapter 7: निर्देशांक ज्यामिति (Coordinate Geometry)
• Next: Chapter 9: त्रिकोणमिति के कुछ अनुप्रयोग (Some Applications of Trigonometry)
• English medium: Class 10 Maths Chapter 8 PDF in English
• All Mathematics (Ganit — Hindi Medium) chapters and the other Class 10 books: Class 10 NCERT books 2026-27
• All Class 1 to 12 NCERT Textbooks: NCERT Books PDF (Class 1–12)
• Every book chapter by chapter: NCERT chapter wise PDF

FAQ

What are the three fundamental trigonometric identities in Class 10 Maths?
(1) sin² A + cos² A = 1; (2) 1 + tan² A = sec² A (for 0° ≤ A < 90°); and (3) 1 + cot² A = csc² A (for 0° < A ≤ 90°).

What are the values of sin 30°, sin 45°, sin 60° and tan 45°?
sin 30° = ½, sin 45° = 1/√2, sin 60° = √3/2, and tan 45° = 1.