Question

Prove the following identity. {Class 10, Introduction to Trigonometry}​

Answer 1

Perimeter is the distance around a closed figure whereas area is the part of the plane occupied by the closed figure.  

The perimeter of the following geometrical shapes are discussed in the first section:

Square

Perimeter of a square = 4 × side

Rectangle​

Perimeter of a rectangle = 2 × (length + breadth)

The section is divided into two sub-parts:

1. Triangles as parts of rectangles

2. Generalising for other congruent parts of rectangles

Before moving onto exercise 11.2, the topics Area of triangle and parallelogram are discussed.  

Area of a square = side × side

Area of a rectangle = length × breadth

Area of a parallelogram = base × height

Area of a triangle =1/2 × base × height  

In the other half of the chapter, circles are explained. The topic is explained in two parts:

1. Circumference of Circle

The distance around a circular region is known as its circumference.  

Circumference of a circle = πd

​​2. Area of circle​

Area of circle is given by πr2