Exploring Triangles: Classify, Fold & Calculate
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Exploring Triangles: Classify, Fold & Calculate
Year 7 Mathematics - Geometry Classification by sides and angles Hands-on paper folding activities Area and perimeter calculations
What Makes a Triangle Special?
A polygon with exactly 3 sides 3 vertices (corners) and 3 angles The angles always add up to 180° Found everywhere in construction and design Strong, stable shape used in bridges and buildings
Classifying Triangles by Their Sides
Equilateral: All 3 sides are equal length Isosceles: 2 sides are equal length Scalene: All 3 sides are different lengths We can measure sides to determine the type Each type has special properties
Classifying Triangles by Their Angles
Acute: All angles less than 90° Right: One angle exactly 90° Obtuse: One angle greater than 90° We use protractors to measure angles The largest angle determines the type
Combined Classifications
{"left":"Right isosceles triangle\nAcute equilateral triangle\nObtuse scalene triangle","right":"Right scalene triangle\nAcute isosceles triangle\nObtuse isosceles triangle"}
Paper Folding Triangle Workshop
Each pair gets 6 sheets of colored paper Follow folding instructions to create different triangle types Label each triangle with its classification Measure sides and angles to verify Create: equilateral, isosceles, scalene, right, acute, obtuse
Measuring Your Triangles
Use rulers to measure all three sides Use protractors to measure all three angles Record measurements in your data table Check: Do the angles add up to 180°? Classify each triangle by sides AND angles
Calculating Triangle Perimeter
Perimeter = sum of all three sides P = side a + side b + side c Measure each side carefully in centimeters Example: 5cm + 7cm + 9cm = 21cm Practice with your folded triangles
Calculating Triangle Area
Area = ½ × base × height Height is perpendicular to the base Choose any side as the base Measure the perpendicular height Example: ½ × 6cm × 4cm = 12cm²
Triangle Challenge: Can You Solve This?
A triangle has sides of 8cm, 6cm, and 10cm What type of triangle is this by sides? Calculate its perimeter If the height to the 10cm base is 4.8cm, what's the area? Discuss your method with a partner