"What did the complementary angle say to the…

A “complementary angle” is not necessarily “complimentary,” but there are jokes. A math riddle is:

Q: What did the complementary angle say to the isosceles triangle?
A: Nice legs.

The “legs” of an isosceles triangle are two equal sides. The geometry riddle has been cited in print since at least 2009.

Math Is Fun
Definition of
Complementary Angle
Two Angles are Complementary when they add up to 90 degrees (a Right Angle).
They don’t have to be next to each other, just so long as the total is 90 degrees.

Wikipedia: Isosceles triangle
In geometry, an isosceles triangle is a triangle that has two sides of equal length. Sometimes it is specified as having exactly two sides of equal length, and sometimes as having at least two sides of equal length, the latter version thus including the equilateral triangle as a special case. Examples of isosceles triangles include the isosceles right triangle, the golden triangle, and the faces of bipyramids and certain Catalan solids.

The Milligram (SVSU Regional Mathematics and Science Center, Spring 2009)
Geometry Riddles
(...)
8. What did the complementary angle say to the isosceles triangle?
Nice legs.

Twitter
Nathan McKinney
@nathanmckinney
Replying to @theysaybuild
@theysaybuild @laurenmckinney What did the complementary angle say to the isosceles triangle? Nice legs! #geometryhumor #justwarmingup
6:25 PM · Jan 10, 2011·TweetDeck

Twitter
Sarah Morrison
@morrisonmath
What did the complementary angle say to the isosceles triangle?
Nice legs!
11:27 AM · Mar 2, 2011·Twitter Web Client

Twitter
Montiflor John
@ayMONTIkna
What did the complementary angle say to the isosceles triangle? Nice legs. #manyak
10:29 AM · Oct 27, 2011·Twitter Web Client

Twitter
Alyssa Minnicino
@AlyssaAnnn
What did the complementary angle say to the isosceles triangle? “Nice legs!” HAHAHAHAHA! #Dying #ImANerdAndIDontCare
11:35 AM · Mar 14, 2012·Twitter for iPhone

Twitter
Bob Kostic
@causticbob
Q: What did the complementary angle say to the isosceles triangle?
A: Nice Legs
6:06 PM · Sep 19, 2015·Twitter Web Client

Twitter
JUMI
@WNALDBS
Q:
What did the complementary angle say to the isosceles triangle?
A:
Nice legs you’ve got there.
#jokes #LOL
9:00 PM · Apr 17, 2019·Twitter for Android

“What did the complementary angle say to the isosceles triangle?”/“Nice legs.”