The corner angles of a triangle always make a straight line,
no matter what kind of triangle it is. Angles on a straight
line always add up to 180º, so the corner angles of a
triangle must always add up to 180º, too.
This is true for
every triangle
you could possibly
draw!
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month, and much more.