[填空题]
Eclipses happen on Earthj-1kbm -x:een because(gxr8avbni1 t 8lvro1b v. 6uwmw8 -(r of an amazing coincidence. Calculate, using the information inside the Front Cover, the b-.6a lo8(r1v88 utmvxi 1b nvwgrrw(angular diameters (in radians) of the Sun and the Moon, as seen on Earth. Sun = $rad$ Moon = $rad$