SaiBook.us Geometry

Lesson Example Discussion Quiz: Class Homework

Example

Title: Area of Traiangle

Grade: 8-a Lesson: S1-L2

Explanation: The best way to understand algebra is by looking at some examples. Take turns and read each example for easy understanding.

Examples:

Find the area of a triangle having base is 18cm and height is 12cm.

Step 1a

Given height(h) = 12cm

base of a triangle(b) = 18cm

Therefore, Area of a triangle = \$1/2 b*h\$

⇒ \$(18\times12)/12\$

⇒ \$216/2\$

⇒ \$108\$sq.cm

Explanation: If the height of a triangle is 12cm and the base is 18cm, the area of the triangle is 108 sq.cm as calculated using the formula: \$1/2 x b x h\$.

Find the area of an equilateral triangle of side 12 cm. (√3 = 1.73).

Step 2a

Given the side of a triangle = 12cm

Area of an equilateral triangle = \$√3/4\$ a² square units

⇒ \$√3/4 \times 12 \times 12\$

⇒ \$√3/4 \times 144\$

⇒ \$√3 * \cancel144^36/\cancel4^1\$

⇒ \$1.73 \times 36\$

⇒ 62.28 cm²

Explanation: If the side of an equilateral triangle is 12cm, then the area of an equilateral triangle is 62.28 cm²

Find the height of a triangle whose area is 420 cm² and base is 60 cm.

Step 3a

Given the area of a triangle(a) = 420 cm²

The base of a triangle(b) = 60 cm

Therefore, height of a triangle = \$(2 \times a)/b\$

⇒ \$(2 \times 420)/60\$

⇒ 14cm

Explanation: If the area of a triangle is 420 cm² and the base of a triangle is 60 cm,the height of a triangle is 14cm as calculated using the formula \$(2\times a/b)\$.