How do you measure the length of a curved line using a divider?
If the curved line is an arc of a circle: 1. Set the divider to a spacing that, from each end of the arc, will scribe an arc that crosses the arc you wish to measure, dividing it in two. 2. From each end of the arc, and again from the centre, and with the dividers set to a radius greater than before, strike arcs to form a cross each side of the arc you are measuring. Join the crosses above and below with a straight line. Project these lines below the arc, until they cross. This will be the centre of the circle the arc is part of. 3. Measure the radius of the arc. From that, calculate the perimeter of the circle it is part of. 4. Draw 2 radials from the centre to the outer ends of the arc. Measure the angle between them. 5. Divide the perimeter by 360, then multiply that result by the degrees in the angle measured. That will be the length of the arc.
