$(a)$ Derive adaptive quadrature formula to evalute $\int_a^bf(x)dx$.
$(b)$ Given, $I=\int_0^{\frac{\pi}{4}}cos^2xdx$ compute $S(0,\frac{\pi}{4}),S(0,\frac{\pi}{8})$ & $S(\frac{\pi}{8},\frac{\pi}{4})$. Also verify the error estimate $$\frac{1}{15}\Biggl|S(a,b)-S\left(a,\frac{a+b}{2}\right)-S\left(\frac{a+b}{2},b\right)\Biggr|<\epsilon$$ for this problem.
For $(a)$ I think this may be work$($Theorem $2)$. But What to do with $(b)?$ I haven't mentioned that kind of error bound in my book Numerical Analysis $10$th Edition by Richard L. Burden. How to get that. Ant help will be appreciated.
Thanks in advanced.