Trigonometry Values Pi/5
Use the identity
(1)
Now, let
and
. Then
(2)
(3)
Solving the
Quadratic Equation
for
gives
(4)
Now,
must be less than
(5)
so taking the
Minus Sign
and simplifying gives
(6)
can be computed from
(7)
Summarizing,
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
See also
Dodecahedron
,
Icosahedron
,
Pentagon
,
Pentagram
© 1996-9
Eric W. Weisstein
1999-05-26