1. The problem statement, all variables and given/known data i am suddenly stuck when differentiating. are my concepts right? if we integrate cosx/sinx, then since cosx is the differentiated form of sinx, then integrating d(sinx)/sinx = ln|sinx| so now, if i have : integrate z/(1-z2)1/2 since z is the differentiated form of the denominator(barring the minus sign), (1-z2)1/2, then integrating d((1-z2)1/2)/(1-z2)1/2, shouldn't i get ln (1-z2)1/2 ? but the answer is without the ln, and true enough when i try to differentiate the ln (1-z2)1/2, i don't get back my original function. so where did i go wrong? thanks!