Be thankful. Be very thankful.
(Disclaimer: Sorry… I confess. I like mathematics. But I do sympathize with those who don’t. Hence this post!)
Here’s how some trigonometry things were explained in 1753…
Rule 1 is simple (really) and useful (really)! (Though I can’t tell you why the text says “five cases of oblique-angled triangles”
By the way, I think Mr. Potter mis-spelt “Plane” in his title for the section. But that’s a story for another day. (Think about the expression “plane sailing”, as in “getting that done was plane sailing”. Plane makes better sense than plain if you are going to base your comparison upon something nautical. If you merely want to say it is “ordinary”, why not “as easy as plain horseback riding”, or somesuch? More people were equestrians than were sailors, after all.)
(My ref: f22609a / Lp1210184)