Example 4 - Chapter 4 Class 7 - Expressions using Letter-Numbers (Ganita Prakash)

Transcript

Example 4 We are familiar with calculating the perimeters of simple shapes. Write expressions for perimeters. Perimeter is the length of outline of the shape For shapes, Perimeter = Sum of all sides Let’s look at the perimeter of common shapes Triangle Perimeter = a + b + c Equilateral Triangle Perimeter = a + a + a = 3a Isosceles Triangle Perimeter = b + a + a = b + 2a Square Perimeter = a + a + a + a = 4a Rectangle Circle Semicircle Perimeter = l + b + l + b = 2l + 2b = 2(l + b) Perimeter = Circumference = 2𝜋r Perimeter = 1/2 × Circumference + 2 × Radius = 1/2 × 2𝜋r + 2r = 𝜋r + 2r = r (𝜋 + 2) Sector Perimeter = Length of arc + 2 × radius = θ × r + 2r = r (θ + 2) θ is in Radius