Calculating the Lateral and Total Surface Area of a Cone

The Organic Chemistry Tutor

This math tutorial provides a step-by-step demonstration of how to calculate both the lateral area and total surface area of a cone. Using a specific example with a radius of 5 inches and a height of 12 inches, the narrator guides viewers through the necessary formulas and calculations. The video visualizes the geometry by drawing a cone and labeling the key dimensions, making abstract formulas concrete. A key component of this lesson is the integration of the Pythagorean theorem. Since the problem provides the vertical height rather than the slant height, the narrator shows how to identify the right triangle within the cone to solve for the missing slant height dimension. This connects 2D triangle geometry concepts with 3D solid geometry. The video then proceeds to substitute these values into the standard formulas for lateral area ($\pi rl$) and total surface area (Base Area + Lateral Area). For educators, this video serves as an excellent model for solving multi-step geometry problems. It reinforces the importance of distinguishing between height and slant height—a common student error. The clear, handwritten derivations allow students to follow the logic line-by-line, making it suitable for introducing the concept, reviewing for exams, or providing support for homework assignments involving 3D geometric measurements.