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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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