Question

find the area of a triangle two sides of which are 18cm and 10 cm and the perimeter is 42cm​

Answer 1

Step-by-step explanation:

use perimeter =sum of sides

and find the area by using herons formula

Answer 2

Answer:

Step-by-step explanation:

Given :–

Two sides of a triangle = 18cm and 10cm.

Perimeter of a triangle = 42cm.

To Find :–

Area of a triangle.

Solution :–

We know that,

Area of a triangle =  

Where,

s = Semi perimeter and a, b & c = sides of a triangle.

• s =  

Given, Perimeter = a + b + c = 42.

Semi-Perimeter =  

⟹ 21cm

Value of s = 21

Now, we need to find the value of c,

Perimeter of a triangle = a + b + c

a + b + c = 42

Where,

a = 18cm.

b = 10cm.

Now, put the given values in the formula of perimeter of a triangle.

⟹ 18 + 10 + c = 42

⟹ 28 + c = 42

⟹ c = 42 – 28

⟹ c = 14cm

Value of c = 14cm.

Now, we have to find the area of a triangle.

a = 18cm

b = 10cm

c = 14cm

s = 21

Put all the values in the formula of the area of a triangle.

⟹  

⟹  

⟹  

⟹  

⟹  

⟹  

Hence,

The area of a triangle is 2√11 cm².