This lecture covers the area and perimeter of triangles using different methods, including the base-height formula and Heron’s formula. It also explains step-by-step triangle construction using SSS, ASA, and SAS methods. Students will learn about symmetry in triangles including lines of symmetry and rotational symmetry for equilateral, isosceles, and scalene triangles, along with real-life examples. The lesson includes worksheets and quizzes to practice calculations, constructions, and shape identification.