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Mihai Preda's profile - activity

2021-02-01 07:24:33 +0200 received badge  Popular Question (source)
2013-07-21 06:53:30 +0200 asked a question Trigonometric simplification for distance on a sphere

These are two equivalent equations for distance on a sphere:


dist1(lat1, lat2, dLon)=2*asin(hav(lat1-lat2)+cos(lat1)*cos(lat2)*hav(dLon))

dist2(lat1, lat2, dLon)=acos(sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(dLon))

(According to ) Indeed numerically they evaluate equal.

But why their difference does not simplify to 0?



Am I doing something wrong? Is there a way to have Sage prove the two forms are equivalent, or to transform one to another?