Stuck at part B.
When I directly substitute (3x) for (x) and let f(x)=8/9(root 6) I get the correct answer which is pi/36.
But arent you supposed to let 3x=z and then sub (z/3) for x into the equation?
I'm a bit confused at when to use direct substitution... can someone explain.
If you let $z=3x$, then you're computing $T(z)$ which means you substitute $z$ for $x$ in the expression, not $\frac{z}{3}$.