## Thursday, March 9, 2017

### Unusual morning skies...

Unusual morning skies...  The mountains to both our east (the Wasatch range) and west (the Wellsville range) have clouds over them this morning, and the sun is rising through a notch in the Wasatches.  This caused the Wellsvilles to be very brightly lit this morning, by sunlight pouring through that notch and under the clouds on the Wasatches.  These conditions don't all come together very often!

### Haversine...

Haversine...  Just ran across this trigonometric function in my reading this morning.  I'd never heard of it before.  Turns out there's a boatload of these “vestigial” trig functions. As the author of that post mentions, I learned about sine, cosine, and tangent in high school, then picked up secant, cosecant, and cotangent somewhere along the line.  The rest of these I'd never heard of: versine, vercosine, coversine, covercosine, exsecant, excosecant, haversine, havercosine, hacoversine, and hacovercosine.

The reason why these functions were invented is interesting, too.  It all comes down to the fact that people didn't used to have calculators or computers at their desks, and these functions, provided in tables, saved a great deal of manual computation...