By the definition of a chord, it is a line segment whose endpoints lie on the circle, (and in this case circle is meant by the set of points equidistant from a center point, or as an algebraic term: circumference)
Two of the given points have the same y-value. The midpoint of those two will be on the line of symmetry, as is the vertex. The x-value there is (-1+5)/2 = 2.
The circumference of a circle is 2•3.14(Pi)•R(radius) or 3.14(Pi)•D(diamater). Since we have our diameter, 60, we need to multiply it by Pi. 60Pi is your answer.
