Triangles

MICRO LESSON 1

Triangle Basics

Picture it: Three sticks joined end to end form a triangle.

Simple: A triangle has three sides, three vertices and three angles.

Example: ΔABC.

Quick Check: How many vertices?

MICRO LESSON 2

Angle Sum Property

Picture it: The three interior angles always total 180°.

Simple: This helps find missing angles.

Example: 50°+60°+70°=180°.

Quick Check: Find third angle if two are 40° and 65°.

MICRO LESSON 3

Exterior Angle

Picture it: Extending one side creates an exterior angle.

Simple: An exterior angle equals the sum of two opposite interior angles.

Example: If opposite angles are 50° and 60°, exterior is 110°.

Quick Check: What is a remote interior angle?

MICRO LESSON 4

Congruent Triangles

Picture it: Two triangles may match exactly in shape and size.

Simple: Congruent triangles have equal corresponding sides and angles.

Example: Paper cut-outs that overlap perfectly.

Quick Check: Is same shape alone enough?

MICRO LESSON 5

SSS Congruence

Picture it: Three matching sides guarantee congruence.

Simple: SSS means side-side-side.

Example: 3 cm,4 cm,5 cm triangles match.

Quick Check: What does SSS stand for?

MICRO LESSON 6

SAS Congruence

Picture it: Two sides and the included angle match.

Simple: SAS means side-angle-side.

Example: The angle must be between the known sides.

Quick Check: Can a non-included angle be used in SAS?

MICRO LESSON 7

ASA and RHS

Picture it: Two angles with included side, or right angle-hypotenuse-side, can prove congruence.

Simple: ASA and RHS are standard rules.

Example: Right triangles often use RHS.

Quick Check: Which rule is for right triangles?

MICRO LESSON 8

Triangle Inequality

Picture it: Two sides together must be longer than the third.

Simple: Otherwise the sides cannot close.

Example: 2,3,6 cannot form a triangle.

Quick Check: Can 4,5,9 form a triangle?