a perfect fit
Will the bargain screen still be visible to the
people at the back, 25 meters away?
28
31
30
Hero’s formula:
Area = s (s-a) (s - b) (s - c)
s = a + b + c
2
s = (31 + 30 + 28) / 2 = 44.5
Area = 44.5 (44.5-31) (44.5 - 30) (44.5 - 28)
= 44.5 x 13.5 x 14.5 x 16.5
= 143729 = 379.1 sq meters
Using conventional, 1/2 base x height, Height = 2 x area/base
Height = 2 x 379.1 / 30 = 25.27 m Perfect !
Do this bi
t firs
t then use i
t
in the
ar
ea f
ormul
a.
Combine tools from your toolbox to
get the answer you need.
Use the relationship between sides
and height to estimate angles.
There’s sometimes more than one
way to solve a problem—pick the
way that seems like the least amount
of work!
Draw sketches or graphs, or use your
hands if you’re stuck remembering
what those side-height-base
relationships are.
200 Chapter 4