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Lesson Example Discussion Quiz: Class Homework

Lesson

Title: Perimeter of Triangle

Grade: 8-a Lesson: S3-L3

Explanation: Hello Students, time to learn definitions. Let us take turns and read definitions and explain the pictures. Try to remember or memorize the definitions. Pay special attention to the pictures and communicate in your own words.

Lesson:

Definition: Perimeter of Triangle

The perimeter of a triangle is defined as the sum of the lengths of its three sides.
In mathematical terms, if a triangle has sides of lengths a, b, and c, then the perimeter P is given by:
p = a + b + c

$1$

Explanation: In this image, the perimeter of a triangle is 40cm given the lengths of its sides as 15cm, 18cm and 7cm.

Definition: Equilateral Triangle

An equilateral triangle is a type of triangle where all three sides are of equal length.

Additionally, all three angles in an equilateral triangle are also equal, each measuring 60 degrees.

$2$

Explanation: For an equilateral triangle, multiply one side by 3.

Definition: Isosceles Traiangle

An isosceles triangle is defined by two equal sides and two equal angles opposite those sides.
This means a triangle typically contains two equal sides and two equal angles.

$3$

Explanation: To find a triangle’s perimeter, add up its side lengths (a, b, c). For isosceles triangles, add 2 times the length of one side (a) to find the third side (c). Remember, a, b, and c are side lengths.

Definition: Scalene Traiangle

A scalene triangle is a type of triangle in which all three sides have different lengths.

Additionally, the angles opposite these sides are also of different measures.

$4$

Explanation: I need to find the perimeter of a scalene triangle. The lengths of its sides are 5 cm, 3 cm, and 2 cm, and the total perimeter of the triangle is 10 cm.