Ex 3.3, 10 - Chapter 3 Class 11 Trigonometric Functions

Last updated at August 17, 2026 by

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

part 2 - Ex 3.3, 10 - Ex 3.3 - Serial order wise - Chapter 3 Class 11 Trigonometric Functions

Remove Ads Take short quiz All Quiz and Worksheets
Teachoo Β· Class 11 Explore Class 11

Transcript

Ex 3.3, 10 Prove that sin⁑(𝑛 + 1)π‘₯ sin⁑(𝑛 + 2)π‘₯+cos⁑(𝑛 + 1)π‘₯ cos⁑(𝑛 + 2)π‘₯=cos⁑π‘₯ Solving L.H.S. We know that cos ( A – B) = cos A cos B + sin A sin B Here, A = (n + 1)x ,B = (n + 2)x Hence sin⁑(𝑛+1)π‘₯ sin⁑(𝑛+2)π‘₯+cos⁑(𝑛 + 1)π‘₯ cos⁑(𝑛 + 2)π‘₯ = 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

Davneet Singh's photo - Co-founder, Teachoo

Made by

Davneet Singh

Davneet Singh is an IIT Kanpur graduate and has been teaching for 16+ years. At Teachoo, he breaks down Maths, Science and Computer Science into simple steps so students understand concepts deeply and score with confidence.

Many students prefer Teachoo Black for a smooth, ad-free learning experience.