The function f whose graph passes through (π/4,0)
and whose derivative is log(tanx)sinxcosx is given by
(logtanx)2+π4
12(logcosx)2
12(logsinx)2
12(logtanx)2
f(x)=∫log(tanx)sinxcosx=12(logtanx)2+C0=fπ4=12(log1)2+C⇒C=0