High school mathematics triangle area formula

Bottom and height S=bh/2

Trilateral S=√s(s-a)(s-b)(s-c) where s=(a+b+c)/2.

The included angle between the two sides is S=absinC/2.

Two angles and an edge s = (c 2sinasinb)/[2sin (a+b)]

The circumscribed circle radius R=abc/4S.

Radius of inscribed circle r=S/s