Check sibling questions

Ex 3.3, 10 - Chapter 3 Class 11 Trigonometric Functions (Term 2)

Last updated at March 22, 2023 by

Ex 3.3, 10 - Prove that sin (n + 1)x sin (n + 2)x + cos (n+1)x - Ex 3.3

Ex 3.3, 10 - Chapter 3 Class 11 Trigonometric Functions - Part 2

This video is only available for Teachoo black users

Subscribe Now

Get live Maths 1-on-1 Classs - Class 6 to 12

Book 30 minute class for ₹ 499 ₹ 299

Transcript

E 3.3, 10 Prove that sin ( + 1) sin ( + 2) +cos ( + 1) cos ( + 2) =cos Taking L.H.S. We know that cos ( A B) = cos A cos B + sin A sin B Hence A = (n + 1)x ,B = (n + 2)x Hence sin ( + 1) sin ( + 2) +cos ( + 1) cos ( + 2) = cos [ (n + 1)x (n + 2)x ] = cos [ nx + x nx 2x ] = cos [ nx nx x 2 x ] = cos (0 x ) = cos ( x) = cos x = R.H.S. Hence , L.H.S. = R.H.S. Hence proved

Ask a doubt
Davneet Singh's photo - Co-founder, Teachoo

Made by

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.