can somebody explain me this sentence in the given context, particularly vertex and altitude please? i didn't study maths in english, so an ELI5 would be incredible
it's part of an introduction to a book called "Everything You Always Wanted To Know About Mathematics" by Brendan W. Sullivan 
link to the book, for those interested in reading further:
As I understand this (non-native myself) it's asking for the right triangle, C-D-A.
The vertex of the right angle of that triangle is D. The altitud, should be D-A, since is the longer side.
So it should look like: A
D C
Again, not native, so I might have gotten this all wrong.
The vertex is the point where the two line segments meet to form the 90 degree angle. (The little square). The point labeled capital D on the smaller triangle.
The altitude I believe refers to the “opposite” side of the right triangle which would be the side labeled lower case d in the smaller triangle.
Leaving the “adjacent” side as the line segment labeled lower case f.
Hope this helps🤙🏼
Wouldn't C be a right angel
