Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class

Examples

Example 1

Example 2 Important

Example 3

Example 4

Example 5 Important

Example 6 Important

Example 7 Important

Example 8

Example 9 Important

Example 10

Example 11 Important

Example 12

Example 13

Example 14

Example 15

Example 16 Important

Example 17 Important

Example 18 Important You are here

Example 19

Example 20 Important

Example 21 Important

Example 22 Important

Question 1 Deleted for CBSE Board 2024 Exams

Question 2 Deleted for CBSE Board 2024 Exams

Question 3 Deleted for CBSE Board 2024 Exams

Question 4 Deleted for CBSE Board 2024 Exams

Question 5 Important Deleted for CBSE Board 2024 Exams

Question 6 Deleted for CBSE Board 2024 Exams

Question 7 Important Deleted for CBSE Board 2024 Exams

Chapter 3 Class 11 Trigonometric Functions

Serial order wise

Last updated at May 29, 2023 by Teachoo

Example 18 If sin 𝑥 = 3/5 , cos y = −12/13 , where 𝑥 and y both lie in second quadrant, find the value of sin (𝑥 + y). We know that sin (x + y) = sin x cos y + cos x sin y We know that value of sin x and cos y but we do not know of cos x and sin y Let us first find cos x We know that sin2x + cos2x = 1 (3/5)^2+ cos2x = 1 9/25 + cos2x = 1 9/25 + cos2x = 1 cos2x = 1 – 9/25 cos2x = (25 − 9)/25 cos2x = 16/25 cos x = ± √(16/25) cos x = ± 4/5 Since x is in llnd Quadrant cos x is negative So, cos x = (−𝟒)/𝟓 Similarly, Finding sin y We know that sin2 y + cos2 y = 1 sin2 y = 1 – cos2 y sin2 y = 1 – ((−12)/13)^2 sin2 y = 1 – 144/169 ("Given cos y =" (−12)/13) sin2 y = (169 − 144)/169 sin2 y = 25/169 sin y = ± √(25/169) sin y = ± √((5 × 5)/(13 ×13)) sin y = ± 5/13 sin y = ± 5/13 Since y lies in llnd Quadrant So, sin y is positive ∴ sin y = 5/13 Now, Putting value of sin x , sin y, cos x, cos y in sin (x + y) = sin x cos y + cos x sin y = 3/5 × ((−12)/13) + ((−4)/5) (5/13) = (−12 × 3)/(5 × 13) + ((−4 × 5)/(5 × 13)) = (−36)/65 + ((−20)/65) = (−36 −20)/65 = (−56)/65 Hence, sin (x + y) = (−𝟓𝟔)/𝟔𝟓