【单选题】7 / 8若 fx=+0.12 mf_x=+0.12\,\mathrm{m}fx=+0.12m、fy=−0.09 mf_y=-0.09\,\mathrm{m}fy=−0.09m,则全长闭合差 fff 约为?A0.03 m0.03\,\mathrm{m}0.03mB0.15 m0.15\,\mathrm{m}0.15m正确C0.21 m0.21\,\mathrm{m}0.21mD0.015 m0.015\,\mathrm{m}0.015m参考答案B参考解析f=0.122+0.092=0.15 mf=\sqrt{0.12^2+0.09^2}=0.15\,\mathrm{m}f=0.122+0.092=0.15m。