PQ is the arc of a circle with radius r, making an angle of 50° at the centre of the circle O. Find an expression for the length of PQ?
Arc Length = $$\frac{\theta}{360}\times2\times\pi\times r$$
$$=\frac{50}{360}\times2\times\pi\times r$$
$$=\frac{5\pi}{18}\times r$$
$$=\frac{5\pi r}{18}$$