The diameter of a sphere is four times the focal length of a concave mirror cut from it.

凹面镜如果是从圆球上切下来的，圆球的直径会是凹面镜焦距的四倍。

youdao

Although high hardness sapphire table mirror, only the diamond can cut it in theory, but does not mean that everything is all right, but also to prevent collision and fall break table mirror.

虽然蓝宝石表镜硬度高，理论上只有金刚石才能划伤它，但不代表就万事大吉，还要防止撞击和掉落震碎表镜。

youdao

I'm smiling in the mirror at my new cut and color when suddenly, oy-my teeth seem to need a little color correction of their own.

我对着镜子里的我的新发型微笑着，突然，哦，我的牙齿似乎需要一点颜色校正。

youdao

The surface became a dark mirror as we cut the motors, taking in the guttural whoops, whines, trills and clicks around us.

BBC: Taming the heart of the Peruvian Amazon

The Pensions Regulator has not yet approved this cut in Trinity Mirror's reduced contributions to the scheme.

BBC: Three pension tales: BT, Royal Mail and Trinity Mirror

In the mirror, she looked sharp enough to cut something, hard fixed lines beside her mouth, her eyes too big, her cheekbones jutting like knuckles under her skin, up to her elbows in dirty work, cleaning toilets.

NEWYORKER: Friendly Fire