00:04with respect to W 111 ok. So, I will continue writing this one as partial derivative of
00:16well with respect to sigmoid of z11 into h1 into 1 minus h1 into x1 ok.
00:30So, why I have written h1 into 1 minus h1 because your sigmoid of z11 is nothing but your h1.
00:38And how do I written how have I written this x1 term? What from where this x1 term came?
00:44x1 term came from my third term which is del z11 del omega 111. So, if I see it here
00:59it
01:00is nothing by what was my z111 made up of? Z11 was what was what is this? Now, z11 is
01:08made
01:09up of w111 into x1 plus w211 into x2. Therefore, del z11 with respect to omega 111 is nothing,
01:32but equal to x1. That is the reason I have written this x1 here fine. This equation I will write
01:42as equation number 3 ok. So, and what were we calculating? So, I will just write it here.
01:49Remember what did I get finally, partial derivative of l with respect to w111 is equal to partial
02:02derivative of l with respect to sigmoid of z11. This I have kept as it is. The remaining two terms
02:09I have got the values h1 into 1 minus h1 into x1. So, this is my equation number 3. I
02:16will not write it
02:16there. Equation number 3 I will make it here. So, that there is no confusion ok alright.
02:33Then for finding out the partial derivative of l with respect to w111, we are still left
02:40out with finding out or calculating this term. Next two terms, the other two terms we have
02:45already done. What do I do for that? So, we will try to figure out what it is. Partial derivative
02:52of l with respect to sigmoid of z11 which I will write it as del l by del h1 because
03:03this
03:03is nothing but this is nothing but your h1 value. This can be written as del l by del y
03:14into del
03:17y by del z1 2 into del z12 into h1. So, what I am doing here is I am using
03:29whatever I had done
03:30in my previous step steps. Z12 is nothing but this one. So, this I had used when I was doing
03:38the weight updation or the partial derivative calculations for w112. So, those things now
03:44I will use it. So, we are going in the from the front to the backward direction ok. Now,
03:57we know del l by del y is nothing but 1 by n summation of y minus t this is
04:06from equation
04:091.2. So, the second term. So, this is the first term this is your first term. The second term
04:17what is the
04:19partial derivative of y with respect to z12. What is your z12 sorry what is your y here that
04:35is nothing but sigmoid of z12 ok. Make this one a little clear. Yes. So, this is the first term.
05:05So,
05:09y was nothing but sigmoid of z12 which I have written here and I am taking the derivative
05:16of y with respect to z12. This again I can write as sigmoid of z12 into 1 minus sigmoid of
05:29z12
05:31z12 from equation 1.3 that is nothing but equal to y into 1 minus y. So, second term also
05:46we calculated.
05:47First term we got here, second term also we calculated we are left only with this one the
05:51third term. So, let us see what we can do to find out third term. So, the third term what
06:00was the third
06:01term partial derivative of z12 with respect to h 1. If we see what is my z12 made up of
06:11it is sigmoid
06:13of z11 into w12 plus sigmoid of z21 into w212. So, I will write it plus sigmoid of z31 into
06:25w312.
06:26So, if we take the partial derivative of z12. So, if we take the partial derivative of z12 with respect
06:31to h 1, once again I will write it h 1 here. It is h 2 equal to h 3
06:37here. So, I have to find out here
06:40this one. So, I will just write down once more z12 equal to h 1 into w112 plus h 2
06:50into w212 plus h 3 into w312.
07:00Therefore, if I take the partial derivative of z12. Therefore, if I take the partial derivative of z1,
07:03to have left and then I will write down the Gimme here at the third term you will tell him
07:05it is
07:05after the two to which one. Can you let me Donna bring up with a student at the physical
07:05p3 l. I won LA klm 2. See what I said on this one. It is the P diases of
07:06Z12 ins.
07:06So, leave that the hers to become w411. I welcome my in the rescue of z1, which is
07:06those who are on the database, and the wiem to goes through the bowl. I hope that the
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