[填空题]
Eclipses happen on Earth because of an amazwljtpou.98, atu55)+hvo5cphc o/q me .p xr4ing coincidence. Cefw 0oea -/h1jnm7c8e)7jo khalculate, using the information inside the Front Cover, the angular diameters (in radians) of the Sun and h-o/e e7 h)w8cf ja701onmjkethe Moon, as seen on Earth. Sun = $rad$ Moon = $rad$