Explore the concept of radius and interval of convergence for power series in this comprehensive calculus lecture. Delve into various examples using the ratio test, including cases where the radius of convergence is infinite or zero. Learn how to determine the interval of convergence for specific power series, such as arctan(x) and ln(1+x), with detailed explanations and step-by-step problem-solving. Master these fundamental concepts to enhance your understanding of power series convergence in calculus.