How to use: Calculate triangle area and perimeter using different methods. Select Type: "Area (Base × Height)" for standard calculation, "Area (Heron's Formula)" when you know all three sides, or "Perimeter" to find the sum of all sides. Enter sides A, B, and C as needed. Formulas: Area = ½ × base × height. Heron's formula: Area = √[s(s-a)(s-b)(s-c)] where s=(a+b+c)/2. Perimeter = a+b+c. Applications: land surveying, roof area calculation, structural engineering, navigation triangulation, construction layout. Triangle inequality: sum of any two sides must be greater than third side. Essential for geometry, trigonometry, and practical measurements.