7.10.2.T

FORMULA-2 Area = √ s(s-a) (s-b) (s-c) Where s= (a + b+ c) / 2 FORMULA-3 Area = (√3/4) * a² (Note: This formula is for equilateral triangles.) Suggested examples: Example 1: Find the angles of a parallelogram if one of the angles is 50°. Answer: Perimeter = 5” + 6” + 2” = 13’’ Example 2: Find the area of the below triangle: Answer: Area = ½ x 4” x 6” = 12 inch ² Example 3: Find the area of the below triangle: Answer: a = 3cm, b = 4cm, c = 5 cm S= (a + b + c)/2 = (3 + 4+ 5)/2= 6 Area = √ s(s-a) (s-b) (s-c) = √ 6 x (6 - 3) x (6 - 4) x (6 - 5) = √ 6 x 3 x 2 x 1 = √36 = 6 cm² Example 3: Find the area of the equilateral triangle with side 3 cm: Answer: Area = √3/4 x 3 x 3 = (1.732 x 9)/4 = 3.897 inch ² 4 © 2009 - 2011 tutorco.com 7.10.2. T TOPIC: Triangles Specific Objectives: The student will be able to calculate the Perimeter and Area of various types of Triangles, using formulae. They will also learn to use various properties of the triangle to calculate the Perimeter and Area. What they already know: The student knows: The classification and properties of Triangles. Simple rules of Parallel lines if they know, it will be helpful. Basic knowledge of solving linear equations. Key Concept: PERIMETER: It is defined as the sum of the lengths of the sides of the triangle. FORMULA: Perimeter = L1 + L2 + L3. (Where L1 and L2 and L3 are the lengths of the 3 sides of the triangle). AREA: The area of a plane figure is the surface enclosed by its sides. This is measured in square units i.e. square centimeters (cm²) or square meters. FORMULA-1 Area = ½ x Base x Height