bisector
base
Base of a trapezoid is a geometry term. It starts with the letter b.
mk
width
Angle Apothem AxesAxiom
I think vertex...
nonagon
The word 'boom' can be used as a word for explosion that starts with a b.
centagan: 100-gon
in geometry, width
The word you are looking for is:Trigonometry
How about a decagon which is a ten sided polygon