If the angular diameter of the moon be 30, how far from the eye a coin of diameter `2. 2c m` be kept to hide the moon?

Explanation

Here, angular diameter of the moon, `theta = 30'`

`theta = (30/60)^@ = (30/60**pi/180)^c = (pi/360)^c`

Let the required distance is `r` cm.

The, length of arc ` = rtheta`

Here, length of arc = diameter of coin `=2.2 cm`

`:. 2.2 = r theta`

`=> 2.2 = r(pi/360)`

`=> r = (2.2**360)/pi = (2.2**360)**7/22 = 252 cm`

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