Question

What is the exact length of AB? (photo below)

Answer 1

I don't know an equation so don't do rate this...but if it were me, I would guess between 6(pi) or 8(pi)

Answer 2

As you can see, the central angle for the arcAB is 270°, whilst the radius is 4 units long.

$\bf \textit{arc's length}\\\\ s=\cfrac{\theta \pi r}{180}~~ \begin{cases} r=radius\\ \theta =angle~in\\ \qquad degrees\\ ------\\ \theta =270\\ r=4 \end{cases}\implies s=\cfrac{(270)(\pi )(4)}{180}\implies s=6\pi$