00:01
In this question, we have been given a function f of x equal to summation of a n cos n pi x divided by lambda and this n is varying from 0 to infinity.
00:26
Then we need to prove this a naught is equal to 1 divided by lambda integration of f x dx from 0 to lambda.
00:42
So to prove this, we can write integration of f of x dx from 0 to lambda will be equal to integration of, so we can write f of x dx as summation of a n cos 2 n pi x divided by lambda dx from n equal to 0 to infinity and the limit is from again 0 to lambda.
01:16
Now we can write this as integration of, so here if we put n equal to 0, so this will be a naught multiplied by, now if we put n equal to 0 here, so this whole term will become 0 and cos 0 is 1.
01:31
So we will have only 1.
01:33
Now plus when we put n equal to 1, we will get a 1 multiplied by cos of 2 pi x divided by lambda.
01:47
Then when we put n equal to 2, then we will get a 2 cos of 4 pi x divided by lambda plus and so on up to infinity and then we have dx.
02:08
So now let's integrate this individually.
02:11
So we will get integration of a naught dx from 0 to lambda, then plus a 1 is constant, we will take this out and integration of cos 2 pi x divided by lambda dx and the limit is again from 0 to lambda plus a 2 integration of cos 4 pi x divided by lambda and again limit is from 0 to lambda plus and so on.
02:44
So here we have dx up to infinity.
02:48
So this will be a naught multiplied by x and the limit is from 0 to lambda plus a 1...