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( \operatorname { sin } 3 x + \operatorname { sin } x ) \operatorname { sin } x + ( \operatorname { cos } 3 x - \operatorname { cos } x ) \operatorname { cos } x = 0 |
Answer» <p>LHS = (sin3x+sinx)sinx + (cos3x-cosx)cosx = (2sin2xcosx)sinx + (2sin2x(-sinx))cosx = 2sin2xcosxsinx -2sin2xcosxsinx =0 =RHS</p> | |