hero’s formula to the rescue
Both of these dea
l
wi
th tr
iangle ar
ea.
Let’s work on the triangle tub next. You need to work
backward from area to find side length. Which tool from
your Geometry Toolbox is the best one for this job?
Solution
Hero’s formula is A = s(s-a)(s-b)(s-c).
It finds area in terms of the sides of the
triangle, so it’s a good fit with our problem:
finding perimeter from area.
Y
ou
can
use
this f
ormul
a but
y
ou hav
e t
o do qui
te a lot
of gnarl
y a
lgebra t
o get t
o
the sides. Not our f
avor
i
te
w
ay t
o sp
end time....
Ringing bells but kind of
sketch
y? C
heck out page 196
t
o r
emind y
our
self how t
o
use Hero’s formula.
Congruenc
e
Pythagor
ean
T
heor
em
N, Z, and
F angles
Area =
1/2 base x
height
Hero’s
f
ormul
a
All your toolbox tools are arranged by
subject in a downloadable PDF at
headfirstlabs.com!
Working smarter, not harder is often about choosing the
right tool for the job. Go to www.headfirstlabs.com/geometry to
grab yourself a handy printable reference sheet of
your geometry tools grouped by topic.
290 Chapter 7