2. Classifying triangles
Sec 4.1
Sol:
How many was can you classify a triangle?

3. Angle sums in a triangle
The sum of the measures of the interior angles and exterior angles of a triangle are 180°. Hands on activity

4. Polygon – is a closed figure in a plane that is made up of segments, called sides that intersect only at their endpoints, called vertices. Triangle – is a three sided polygon. You name them by their vertices.
Parts of a triangle
Sides
Vertices
Angles

5. Opposite Sides
The opposite side is the side that is across from the angle. It is the side that has nothing to do with forming the angle. The side opposite A is _____ The side opposite B is _____ The side opposite C is _____

6. Classifying Triangles
There are two ways to Classify Triangles.
1. By their Angles
a. Acute
b. Equiangular
c. Obtuse
d. Right
2. By the number of Congruent Sides they have.
a. Scalene
b. Isosceles
c. Equilateral

7. Acute triangle:
All the angles are Acute (All the angles measures are < (less than) 90°.
Mrs. Acute

8. Equiangular Triangle is a special type of Acute triangle.
All Angles are congruent.
Each angle has a measure of 60°.
Mrs. Equiangular

9. Obtuse Triangles Has only one angle that is obtuse.
This angles has a measure > (greater than) 90° but < (less than) 180°.
Mr. Obtuse

10. Right Triangles Has only one angle that is a right angle.
Meaning only one angle has a measure of 90°.
The sides of a right triangle have special names:
a) The side opposite the right angle is the________________
b) The two sides that form the right angles are the_________
Mrs. Right
Hypotenuse
Legs

11. Use the triangle below, identify the following:
Sides
Vertices
Angles
Hypotenuse
Legs

12. Scalene Triangle No two side are Congruent.
Meaning all the side have different side lengths.
Mr. Scalene

13. Isosceles Triangles
At least two side are congruent.
Mr. Isosceles

14. Like a right Triangle the parts of an Isosceles triangle have special names.
leg
The angle formed by the congruent sides is called the VERTEX ANGLE
The side opposite the vertex the called the BASE
The congruent sides are called LEGS
The two angles formed by the base and one of the congruent sides are called BASE ANGLES.

15. Equilateral Triangles
All the sides are congruent.
Is a special type of Acute triangle.
Is also considered to be Isosceles.
Mr. Equilateral

16. Examples
Triangle PQR is an equilateral triangle. One side measures 2x + 5 and another side measures x Find the length of each side.

17. Given STU, with vertices S(2, 3), T(4, 3) and U(3, – 2) , use the distance formula to prove STU is isosceles.
ST = ______________
TU = ______________
SU = ______________

18. Assignments
Classwork: Workbook Pg: 41 and Homework: Pg