The planets move around sun in elliptical orbits with sun at one focus. Point in orbit at which planet is closest to sun is called perihelion, and point at which it is farthest is called aphelion. These points are vertices of orbit. Planet's distance from sun is 55,000,000 km at perihelion and 61,000,000 km at aphelion. Determine the equation for planet's orbit. Place origin at the center of orbit with sun on x-axis.