常見例句The sun appears to move in an arc across the sky.太陽(yáng)看起來(lái)在天空以弧線運(yùn)行。An early instrument for measuring altitude of celestial bodies, consisting of a90= graduated arc with a movable radius for measuring angles.象限儀用來(lái)測(cè)量天體緯度的一種早期工具，由一個(gè)有90度刻度的圓弧和一個(gè)用來(lái)測(cè)量角度的可移動(dòng)的半徑構(gòu)成 返回 arcing