Astronomers discover an exoplanet (a planet of a star other than the sun that has an orbital period of 3.41 earth years in its circular orbit around its sun, which is a star with a measured mass of 3.13 × 1030 kg. find the radius of the exoplanet\'s orbit.
You would most definitely use Kepler's third law. With almost all planets, the mass of the planet is negligible so it is ignored.We know the orbital period and the mass. Use those and Kepler's third law to write an equation for the orbital radius.