# Lesson Notes By Weeks and Term - Senior Secondary 1

Triangles

TERM – 1ST TERM

WEEK NINE

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Technical Drawing

Topic: TRIANGLES

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

I.) Define a triangle

II.) Identify the types of triangles and draw them out.

III.) Describe the general procedure for constructing triangles.

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

 PRESENTATION TEACHER’S ACTIVITY STUDENT’S ACTIVITY STEP 1 INTRODUCTION The teacher identify the types of triangles and draw each on the board Students listens attentively to the teacher STEP 2 EXPLANATION Teacher discusses the general procedure for constructing triangles. Students exhibit attentiveness and active engagement STEP 3 NOTE TAKING The teacher writes a summarized note on the board The students copy the note in their books

NOTE

TRIANGLES

A triangle is a polygon with three sides and three angles. It's one of the basic shapes in geometry. They have unique properties, such as the sum of their interior angles always totaling 180 degrees.

Types of triangles

1. Scalene Triangle: A scalene triangle is a triangle in which all three sides have different lengths. Since the lengths of all sides are different, the angles opposite these sides are also different.

2. Isosceles Triangle: An isosceles triangle is a triangle with at least two sides of equal length. Consequently, the angles opposite the equal sides are also equal. Isosceles triangles have some interesting properties, such as the altitude from the vertex angle bisecting the base and the median from the vertex angle coinciding with the altitude and angle bisector.

3. Equilateral Triangle: An equilateral triangle is a triangle in which all three sides are equal in length. Since all sides are equal, all three angles are also equal, each measuring 60 degrees.

Equilateral triangles are symmetrical and have many interesting properties, such as having equal medians, altitudes, and angle bisectors.

4. Right-Angled Triangle: A right-angled triangle is a triangle in which one of the angles is a right angle, measuring exactly 90 degrees. The side opposite the right angle is called the hypotenuse, and it's the longest side in the triangle.

Construction of Triangles

To construct a triangle, there are three simple items that must be available. They are:

- Three sides of the triangle must be given.

- Two sides and one angle must be given.

- One side and two internal angles must be given.

EVALUATION: 1. Using the procedure above, construct the following triangles:

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively