Terrio's Reflection

So I was flipping through my binder and I came across a bunch of old formulas that I almost forgot about. Here they are:

Area of a non-right triangle
A=1/2(leg)(leg)sin(angle between)

Area of Right Triangles
A=1/2bh

SOHCAHTOA
sinΘ=opposite leg/hypotenuse
cosΘ=adjacent leg/hypotenuse
tanΘ=opposite leg/adjacent leg

Law of Sines
sinA/a - sinB/b = sinC/c
(used when you know pairs or opposites in a non-right triangle)

Law of Cosines
(opposite leg)²=(adjacent leg)² + (other leg)² - 2(adjacent leg)(adjacent leg)cos°

Area of Inscribed Shapes
A=nr²sinΘcosΘ

Now I know how to use most of these, but the area of Inscribed Shapes is kind of fuzzy to me. I don't even remember learning about that