1. 4-1 Classifying triangles
Ch. 4 Test Tuesday Nov. 25th *
*If you leave early for Thanksgiving, take the test BEFORE you go!!

2. TYPES OF TRIANGLES (BY ANGLES)
Acute Obtuse Right Equiangular
All acute angles
1 obtuse angle
1 right angle
3 congruent angles

3. Example Classify the triangle as acute, equiangular, obtuse, or right.
Answer: 3 congruent angles so it’s an equiangular triangle.

4. Example Classify the triangle as acute, equiangular, obtuse, or right.
Answer: One angle of the triangle measures 130°, so it is an obtuse triangle.

5. TOO
The frame of this window design is made up of many triangles. Classify ΔACD.
A. acute
B. equiangular
C. obtuse
D. right

6. Example
Classify ΔXYZ as acute, equiangular, obtuse, or right. Explain your reasoning.
m<XYZ = = 90.
Answer: Since ΔXYZ has a right angle, it is a right triangle.

7. TYPES OF TRIANGLES (BY SIDES)
Scalene Isosceles Equilateral
The base is the
non-congruent side
No congruent sides
2 congruent sides
3 congruent sides

8. Example
If point Y is the midpoint of VX, and WY = 3.0 units, classify ΔVWY as equilateral, isosceles, or scalene. Explain your reasoning.
By the definition of midpoint, VY = YX.
VY= 4.2
So, VW = 4.5 units, WY = 3.0 units, and VY = 4.2 units.
Answer: Since all three sides have different lengths, the triangle is scalene.

9. TWAP
The frame of this window design is made up of many triangles. Classify ΔABC. Be ready to justify your answer
A. isosceles
B. equilateral
C. scalene
D. right

10. TOO
If point C is the midpoint of BD, classify ΔABC as equilateral, isosceles, or scalene.
A. equilateral
B. isosceles
C. scalene

11. Example
ALGEBRA Find the measures of the sides of isosceles triangle KLM with base KL. __
Find d.
KM = ML
4d – 13 = 12 – d
5d – 13 = 12
5d = 25
d = 5 Are we done????
NO!! Find the sides.

12. Example continued Step 2 Substitute to find the length of each side.
KM = 4d – 13
= 4(5) – 13 or 7
ML = KM
KM = 7
KL = d + 6
= or 11
Answer: KM = ML = 7, KL = 11

13. TWAP
Find x and the measure of each side of equilateral triangle ABC if AB = 6x – 8, BC = 7 + x, and
AC = 13 – x.
A. x = 10; all sides are 3.
B. x = 6; all sides are 13.
C. x = 3; all sides are 10.
D. x = 3; all sides are 16.

14. Homework Pg. 241-243 #15-20 all, 21-35 Odd, 36, 37, 43*, 44*, 56-59
*Graph paper!