You can take this web pages word for it that the moon is about 383,000 km from the earth and the sun is 149,600,000 km from the earth.  Or you could check out the distances as well as other Astological Distances at this web site.

When you use your hand to find the angle of sky occupied by the sun and the moon you find that both are about 0.5 degrees.  This is why they look like they are the same size.  However, now that you understand small angle approximation you'll discover the sun is significantly bigger.

(0.5 degrees)/(57.3 degrees/radian)= 0.00872 radians

We know the distance to the object multiplied by the numbers of radians the object occupies in the sky equals the diameter of the object.

Diameter of moon= 0.00872*383,000km= 3,340 km
Diameter of sun= 0.08872*149,600,000 km = 1,304,512 km

A quick search on line will show that these numbers are not far off and that small angle approximation does work.  The sun, as we know, is much bigger than the moon.

Let's see how Chandra and small angle approximation can help you find out more about celestial objects.
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