How to deactivate Monthly Masti service, BSNL ?

I used to get a SMS every month, from BT -ONMOBL, saying :

" Thank You for continuing Monthly Masti service. You have been charged Rs5. For other exciting subscription packs details, SMS HELP SUB to 56505. "

But I've not subscribed to any of such services. Its very hectic and fraud. BSNL is grabbing the money from consumers without any consent of the consumer. Searched this in internet, and to my surprise I found that, there are many people like me, who are facing the similar problem. Somewhere in the internet, found a way to unsubscribe it.

To Unsubscribe :  Send CAN MASTI  to  56505. Then they will ask for your confirmation to unsubscribe, by sending the following SMS to you.

" Dear subscriber, To confirm your cancellation please send  
 CAN  MASTI  YES  to  56505 "

That's great. To activate the pack, they won't ask for your confirmation, but they strictly need it to deactivate it. And for each of  these SMS s, they will charge 2 Rs. But any way, 2+2 Rs. is better to loose than 5 Rs./month. Is n't it ?

Praise the BSNL..!!

How can we prove Cauchy-Goursat theorem ?

Cauchy - Goursat theorem says, the integral of an analytic function  f(z) over a closed contour C ,  is zero. Mathematically,

 

( Function has to be analytic at all the interior points and on the contour C as well.)

To prove this, let's start with an analytic function f(z). Consider

 where C is any simple closed contour in the Z-plane. By knowing  
f(z) = u(x,y) + i v(x,y), and dz = dx + i dy , the above integral becomes 

 

where vectors V_1 = (u, -v) , V_2 = (v, u) and dr = (dx, dy).
Now, the two closed loop integrals on the right hand side can be converted into surface integrals, by using Stokes theorem. Hence, we can write,

 

 We can realize that these two integrands goes to zero, since the function  f(z), is an analytic function. Hence it satisfies the Cauchy-Riemann conditions,

So, for an analytic function, it is guaranteed that,

 

which implies

 

Hence the theorem is proved.