Question

1.54. The relations considered in this problem are used on many occasions throughout the book. (a) Prove the validity of the following expression: (d) Evaluate assuming that |a| < 1. ΣN-1 { N a= 1 Lan = 1-a^N, n=0 1-a for any complex number a ≠ 1. This is often referred to as the finite sum formula. (b) Show that if |a| < 1, then ∞ Σ Lan= 1-a^n. n=0 This is often referred to as the infinite sum formula. (c) Show also if |a| < 1, then ∞ Σ2.:nan = _ _a_-=- n=0 (1 - a)^2.

          1.54. The relations considered in this problem are used on many occasions throughout the book.
(a) Prove the validity of the following expression:
(d) Evaluate
assuming that |a| < 1.
ΣN-1 { N a= 1
Lan = 1-a^N, n=0 1-a
for any complex number a ≠ 1.
This is often referred to as the finite sum formula.
(b) Show that if |a| < 1, then
∞ Σ Lan= 1-a^n.
n=0
This is often referred to as the infinite sum formula.
(c) Show also if |a| < 1, then
∞
Σ2.:nan = _ _a_-=- n=0 (1 - a)^2.
        
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Added by Tamara F.

Computer Science and Information Technology
Computer Science and Information Technology
Trishna Knowledge Systems 2018 Edition
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1.54. The relations considered in this problem are used on many occasions throughout the book. (a) Prove the validity of the following expression: (d) Evaluate assuming that |a| < 1. ΣN-1 { N a= 1 Lan = 1-a^N, n=0 1-a for any complex number a ≠ 1. This is often referred to as the finite sum formula. (b) Show that if |a| < 1, then ∞ Σ Lan= 1-a^n. n=0 This is often referred to as the infinite sum formula. (c) Show also if |a| < 1, then ∞ Σ2.:nan = _ _a_-=- n=0 (1 - a)^2.
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Transcript

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00:01 So, in a part of the question, we are given that z is equal to r into e to the power i theta, where r is less than 1.
00:09 So, therefore, summation from n equals to 0 to infinite of z to the power n will be equals to summation from n equals to 0 to infinite of r into e to the power i theta to the power n, which will be equals to summation from n equals to 0 to infinite of r to the power n e to the power i n theta.
00:32 And from here, we can write this thing will be equals to r to the power 0 e to the power 0 plus r e to the power i theta plus plus r square e to the power 2 i i theta plus r to e to the power 3 i theta and plus up to so on.
00:50 And from here, we will get that this is equals to 1 plus r to the power e i theta plus r square e to the power 2 i theta plus up to so on.
00:58 We will consider this first.
01:00 So now we can find this as we know that sum of infinite term is equals to a divided by 1 minus r.
01:08 So where a is equals to 1 and r equals to r into e to the power i theta.
01:13 So now we are using that e to the power i theta is equals to cos theta plus i sin theta...
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