#NEWLINE# def _eval_expand_trig( self , **hints ) : #NEWLINE# #INDENT# from sympy.functions.special.polynomials import chebyshevt #NEWLINE# arg = self . args [ 0 ] #NEWLINE# x = None #NEWLINE# if arg . is_Add : #NEWLINE# #INDENT# ( x , y ) = arg . as_two_terms ( ) #NEWLINE# sx = sin ( x , evaluate = False ) . _eval_expand_trig ( ) #NEWLINE# sy = sin ( y , evaluate = False ) . _eval_expand_trig ( ) #NEWLINE# cx = cos ( x , evaluate = False ) . _eval_expand_trig ( ) #NEWLINE# cy = cos ( y , evaluate = False ) . _eval_expand_trig ( ) #NEWLINE# return ( ( cx * cy ) - ( sx * sy ) ) #NEWLINE# #UNINDENT# else : #NEWLINE# #INDENT# ( coeff , terms ) = arg . as_coeff_Mul ( rational = True ) #NEWLINE# if coeff . is_Integer : #NEWLINE# #INDENT# return chebyshevt ( coeff , cos ( terms ) ) #NEWLINE# #UNINDENT# pi_coeff = _pi_coeff ( arg ) #NEWLINE# if ( pi_coeff is not None ) : #NEWLINE# #INDENT# if pi_coeff . is_Rational : #NEWLINE# #INDENT# return self . rewrite ( sqrt ) #NEWLINE# #UNINDENT# #UNINDENT# #UNINDENT# return cos ( arg )