SymPy Gamma

Input:

plot (y =x ,y1 =x ^2 ,r =cos (zeta ),r1 =sin (zeta ))

Error:

plot (y =x ,y1 =x ^2 ,r =cos (zeta ),r1 =sin (zeta ))

unbound method could_extract_minus_sign() must be called with zeta instance as first argument (got nothing instead)

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