[填空题]
Eclipses happen on Earth because of an amazin9 jxhmx1p;y8u w h z+/on-lco;g coincidence. Cf d;.aq*ww2be.l9jit vko 3h9alculate, using the information inside the Front Cover, the angular diameters (in radians) of the Sun and the Moon,bk fw htq ve93.;2 o.9diwal*j as seen on Earth. Sun = $rad$ Moon = $rad$