Suppose a function F(z) is a product of \"n\" differentiable functions: F(z)=f1(z)f2(z)f3(z)...fn(z). Find F\'(z)/F(z) in simplest form. (Its F prime in the numerator. Its not very clear because of the font.) Solution F(z)=f1(z)f2(z)f3(z)...fn(z) while differentiating one function will be differentiated and others will remain constant F\'(z)=f1\'(z)f2(z)f3(z)...fn(z) + f1(z)f2\'(z)f3(z)...fn(z) + f1(z)f2(z)f3\'(z)...fn(z) .................. + f1(z)f2(z)f3(z)...fn\'(z) F\'(z)/F(z) = [ f1\'(z)f2(z)f3(z)...fn(z) + f1(z)f2\'(z)f3(z)...fn(z) + f1(z)f2(z)f3\'(z)...fn(z) .................. + f1(z)f2(z)f3(z)...fn\'(z)]/[f1(z)f2(z)f3(z)...fn(z)] F\'(z)/F(z) = f1\'(z)/f1(z) + f2\'(z)/f2(z) + f3\'(z)/f3(z) + ...................... + fn\'(z)/fn(z).