00:01
Hi, in this question, given that the function f of x is defined in the interval 0, 4 and it is 1 by 4 x, 0 less than x and x less than or equal to 2 and here 0 when 2 less than x and x less than 4.
00:22
So, here the function is approximated by the fourier series f of x equals a naught plus summation n equals 1 to infinity a n cos n pi x divided by l plus b n sin n pi x divided by l.
00:42
So, here we need to use the fact f of x and f of x cos n pi x divided by l are odd function.
00:50
So, that we can conclude that the value of a n equals 0 for n equals 0, 1, 2 and etc.
01:01
Next, we have to find the coefficients of b n.
01:07
We know that b n equals 2 by l integral over 0 to l f of x sin n pi x divided by l into dx.
01:14
On substituting l in this, then we get 2 by 4 integral over 0 to 4 f of x sin n pi x divided by l into dx.
01:21
On substituting the corresponding functions, then we get 1 by 2 integral over 0 to 2, 1 by 4 x sin n pi x divided by 4 dx integral over 2 to 4 0 sin n pi x divided by 4 into dx.
01:33
So, that we can write it as 1 by 8 integral over 0 to 2 x sin n pi x divided by 4 into dx.
01:40
We need to solve this integration.
01:42
So, that we have to use the formula u dv.
01:46
So, consider u equals x and integral dv equals integral sin n pi x divided by 4 into dx.
01:52
U dash equals 1 and u double dash equals 0 and v1 equals minus 4 by n pi cos n pi x divided by 4...