The given trigonometric expression is,
tan −1 ( x y )− tan −1 x−y x+y
Simplify the given expression,
tan −1 ( x y )− tan −1 x−y x+y = tan −1 ( x y − x−y x+y 1+( x−y x+y )( x y ) ) = tan −1 ( ( x+y )x−y( x−y ) y( x+y ) y( x+y )+x( x−y ) y( x+y ) ) = tan −1 ( x 2 +xy−xy+ y 2 xy+ y 2 + x 2 −xy ) = tan −1 ( x 2 + y 2 x 2 + y 2 )
Simplify further,
tan −1 ( x y )− tan −1 x−y x+y = tan −1 1 = π 4
Therefore, option © is correct.