00:01
Hello students, the given function is f of z equal to cos z by z square minus 1 the whole square.
00:09
Here we have to find the residue of f of z at z naught equal to minus 1.
00:20
Here it is of order 2.
00:31
We know that if z equal to z naught is a pole of order m, then the residue of f of z at z equal to z naught is 1 by m minus 1 factorial into d power m minus 1 by d z power m minus 1 into z minus z naught the whole power m into f of z at z equal to z naught.
01:20
Therefore we have to apply the values here that is here m equal to 2 and z naught is minus 1.
01:34
Therefore, residue of f of z is 1 by 2 minus 1 factorial into d by d z of z plus 1 the whole square.
01:51
The given function is cos z by z square minus 1 the whole square.
02:01
Here z equal to z naught.
02:02
So, let us take it as z equal to minus 1.
02:05
Therefore, 1 by 1 factorial that is 1 into d by d z of z plus 1 the whole square into cos z.
02:16
Here we can elaborate this.
02:18
Therefore, it will be z minus 1 the whole square z plus 1 the whole square at z equal to minus 1.
02:31
Therefore, we will get d by d z of this will get cancelled...