dāng / yuánxīnjiǎo / dàyú / yìbǎibāshídù / shí / tā / suǒduì / de / hú / jiùshì / yōuhú

当圆心角大于一百八十度时，它所对的弧就是优弧。

When the central angle is greater than 180 degrees, the arc it subtends is a major arc.