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...