`cos x+cos 2x+...+cos nx = sin((nx)/2) cosec(x/2)cos (((n+1)x)/2)`
3,711 views · Published 13 October 2018 · 3:59 · Indexed 4 October 2026
Channel: Doubtnut · 2018 · Education
To ask Unlimited Maths doubts download Doubtnut from - https://goo.gl/9WZjCW `cos x+cos 2x+...+cos nx = sin((nx)/2) cosec(x/2)cos (((n+1)x)/2)`
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