f(π/2)-f(0)=1
F(π/2)-f(0)=π/2-1
[F(π/2)-F(0)]/[f(π/2)-f(0)]=π/2-1
g(x)=F`(x)/f`(x)=secx-tanx
g`(x)=tanxsecx-sec^2(x)=sec(x)[tanx-secx]
f(π/2)-f(0)=1
F(π/2)-f(0)=π/2-1
[F(π/2)-F(0)]/[f(π/2)-f(0)]=π/2-1
g(x)=F`(x)/f`(x)=secx-tanx
g`(x)=tanxsecx-sec^2(x)=sec(x)[tanx-secx]