Okay - this one’s math, but for those who like to geek out about even minor nerdy things …
So I’ve been teaching geometry to high schoolers for a lot of years now (cough - ‘decades’ - cough), and only just this morning I learned this cool new term! (Thanks to the Gemini AI for the answer…)
So most high school students should be able to tell you that any two angles adding to 90 degrees are complementary angles. And any angles adding to 180 degrees are supplementary angles. But is there a word for two angles that add to 360 degrees? Turns out … yes there is: explementary angles! (Or ‘conjugate’ angles - if you find the first word a mouthful.) So the green and lavender angles below are explementary!
Or maybe they could more specifically be called a ‘conjugate pair’ (Sorta like two adjacent supplementary angles are called a linear pair.) I mean - I knew what a ‘reflex’ angle is - any angle larger than 180 degrees. But in the process of grading tests and challenging students to identify sets of adjacent angles, it occurred to me that an astute student could argue that their three letter angle identification was really meant to refer to the reflex angle rather than the standard (less than 180 degree) one! (None have done so.) But it did set me to wondering how would one identify the conjugate angle - since it involves the same three letters and the same vertex? Turns out you have to add the word ‘reflex’ in front of your angle symbol - otherwise it is assumed you are referring to the less-than-180-degree angle.
If you read this far, your high school geek street cred is more-than-intact!