Avem sirul:
tg 45o, tg 22o 30’, tg 11o 55’, ….. an
Sa se afle termenul general an = ?
Π / 4 = 180 / 4 = 45o
Π / 8 = 180 / 8 = 22o 30’
adica facem impartirea:
180 o : 8
16 22o 30’
20
16
4
o = 240’ (arcminute)
24
= 0
Π / 12 = 180 / 12 = 11o 55’
Π / 4, Π
/ 4 / 2, Π / 4 / 2 / 2 … an
adica:
Π / 4, Π
/ 8, Π / 16, Π / 32, Π / 64 … an
Se mai poate scrie si altfel:
Π / 4*1,
Π / 4*2, Π / 4*4, Π / 4*8, Π /
4*16 … an
dar stim ca:
sirul 1, 2, 4, 8, 16……….an
are termenul general an = 2n-1
1, 2, 4, 8, 16……….2n-1
astfel inlocuind =>
Π / 4 = Π / 4*1 = Π / 4*2n-1
=>
Π / 4*1,
Π / 4*2, Π / 4*4, Π / 4*8, Π /
4*16, …… Π / 4*2n-1
deci rezulta in final ca sirul:
tg 45o, tg 22o 30’, tg 11o 55’, ….. an
are termenul general: