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Ex 3.3, 19 - Prove sin x + sin 3x / cos x  + cos 3x = tan 2x - cos x + cos y formula

Ex 3.3, 19 - Chapter 3 Class 11 Trigonometric Functions - Part 2

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Ex3.3, 19 Prove that sin x + sin 3x /( x + 3x ) = tan 2x Taking L.H.S. sin x + sin 3x /( x + 3x ) We solve sin x + sin 3x & cos x + cos 3x seperately Now + 3 / + 3 = (2 2x ( ) )/(2 2 ( ) ) = 2x /cos 2x = tan 2x = R.H.S Hence L.H.S = R.H.S Hence proved

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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.