S=ln((1+t)/(1-t))S'=(1-t)/(1+t) * ((1+t)/(1-t))' = (1-t)/(1+t) * (1(1-t)+1(1+t))/(1-t)^2 = 1/(1+t) * (1-t + 1 + t)/(1-t) = 1/(1+t)*2/(1-t)=2/(1-t^2) S'(3)=2/(1-9)=2/-8=-1/4=-0.25
S=ln((1+t)/(1-t))
S'=(1-t)/(1+t) * ((1+t)/(1-t))' = (1-t)/(1+t) * (1(1-t)+1(1+t))/(1-t)^2 = 1/(1+t) * (1-t + 1 + t)/(1-t) = 1/(1+t)*2/(1-t)=2/(1-t^2)
S'(3)=2/(1-9)=2/-8=-1/4=-0.25