The area of the sector formed by joining the tips of r2 and r3 around the orbit is B1. The area of the sector formed by joining the tips of r1 and \(\tex...The area of the sector formed by joining the tips of r2 and r3 around the orbit is B1. The area of the sector formed by joining the tips of r1 and r2 around the orbit is B3. Our aim is to use this approximate Equation to find approximate values for the heliocentric distances at the instants of the three observations, and then to refine them in order to satisfy the exact Equation 13.2.5.