Head First 2D Geometry

you are here 4 303

regular polygons

What do we need to know about

the polygon triangles?

We know that there are the same number of triangles as sides of

the polygon, and we know that all the triangles are congruent so

we just need to find the area of one. But what else do we need to

know to find the triangle’s area, so that we can combine them to

find the total polygon area?

b

b

h

a

c

Area =

1/2 base x

height

Hero’s

formula

Well, we used the fact that a circle is

like a polygon to find the circle area formula.

So, doesn’t that mean that a polygon is like a

circle, too? Or at least there’s a connection

between circles and polygons and these

triangle segments? Could that help?

That’s an interesting connection.

If a circle is like a polygon, the reverse must also be true

on some level: a polygon is (kinda) like a circle. Maybe

this idea can help us find what we need to calculate the

polygon area and choose the perfect hot tub?

area?

base?

height?

side a?

side b?

side c?

Where do we get

these?

Where do we get

these?

304 Chapter 7

geometry detective

Hint: Start by dividing the polygons into equal triangles.

You’re looking for base, height, and side length of those.

Geometry Detective

Your mission is to investigate how you could find the missing information

needed to use either of the triangle area ...