Expression 3: "f" left parenthesis, negative 8 Superscript, StartFraction, negative "a" Over pi , EndFraction , Baseline left parenthesis, "x" cos "a" minus "y" sin "a" , right parenthesis , 8 Superscript, StartFraction, negative "a" Over pi , EndFraction , Baseline left parenthesis, "x" sin "a" plus "y" cos "a" , right parenthesis , right parenthesis less than or equal to 0f−8−aπxcosa−ysina,8−aπxsina+ycosa≤0