[填空题]
Eclipses happen on Earmmu+ c70ca3(u f-qn osedin; vc,:3xwe*u46gvv/hr r0 pphc *th because of an amazing coincidence. Calculate, using the information inside the Front Cover, the angular diameters (in radians) of the Sun and t3vc,e6wuhr enh 40vcxi/ g:v* pr*d;p he Moon, as seen on Earth. Sun = $rad$ Moon = $rad$