I have a summation within a summation in the above expression. What is its value?
Details and Assumptions :
is an imaginary number such that
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First we take ∑ q = 1 1 0 ( s i n 1 1 2 q π − i c o s 1 1 2 q π )
= − i ∑ q = 1 1 0 ( c o s 1 1 2 q π + i s i n 1 1 2 q π )
= − i ∑ q = 1 1 0 ( e i 1 1 2 π ) q
= − i ∑ q = 1 1 0 α q , w h e r e α = e i 1 1 2 π
= − i 1 − α α ( 1 − α 1 0 )
= − i 1 − α ( α − α 1 1 )
= − i 1 − α α − 1 b c z e i 1 1 2 π × 1 1 = e i 2 π = 1
⟹ ∑ q = 1 1 0 ( s i n 1 1 2 q π − i c o s 1 1 2 q π ) = i − − − − − − − − − ( 1 )
Now ,
∑ p = 1 3 2 ( 3 p + 2 ) [ ∑ q = 1 1 0 ( s i n 1 1 2 q π − i c o s 1 1 2 q π ) ] p
= ∑ p = 1 3 2 ( 3 p + 2 ) i p , u s i n g ( 1 )
= 3 ∑ p = 1 3 2 p i p + 2 ∑ p = 1 3 2 i p = 3 A + 2 B − − − − − ( 2 )
where A = i + 2 i 2 + 3 i 3 + . . . . . . + 3 2 i 3 2
∴ A i = i 2 + 2 i 3 + 3 i 4 + . . . . . . + 3 1 i 3 2 + 3 2 i 3 3
∴ A ( 1 − i ) = ( i + i 2 + i 3 + i 4 + . . . . . . + i 3 2 ) − 3 2 i 3 3
⟹ A ( 1 − i ) = − 3 2 i
⟹ A = ( 1 − i ) − 3 2 i = 1 6 ( 1 − i ) − − − − − − − − − − − − − − ( 3 )
B = i + i 2 + i 3 + i 4 + . . . . . . + i 3 2 = 0 − − − − − − − − − − − − ( 4 )
( 3 ) a n d ( 4 ) i n ( 2 ) ⇒
∑ p = 1 3 2 ( 3 p + 2 ) [ ∑ q = 1 1 0 ( s i n 1 1 2 q π − i c o s 1 1 2 q π ) ] p = 4 8 ( 1 − i )