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December 21, 2014

December 21, 2014

Posted by **Doug** on Monday, September 28, 2009 at 11:07pm.

I need to find what A, B, and C equal. Thanks.

- Math -
**drwls**, Monday, September 28, 2009 at 11:20pmThe sum of the length of the longest day and the shortest day should be 24 hours. The mean has to be 12.

Assuming instead that the numbers are 7 and 18, as your problem states, the formula would be

D (daylight hours) =

12.5 + 5.5 sin (2 pi t/365)

where t is measured in days from the vernal equinox (June 21 in the northern hemisphere)

If you want to measure t from January 1, you will have to do a transformation and include a cosine term

- Math (correction) -
**drwls**, Monday, September 28, 2009 at 11:22pmThe formula I gave is correct, but the vernal equinox (from which t is measured) is March 21.

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