1. Warm-up Classify each angle: 1. 2. 3. 4. Solve for x.
4. Solve for x.
(6x + 2) + (3x + 5) + (x + 3) = 180

2. Triangles and Angles Unit 4 Triangle Properties Section 4.1
Slides
Section 4.1

3. Triangles can be classified in two ways:
Angle measures
Right
Acute
Obtuse
Side lengths
Scalene
Equilateral
Isosceles

4. Classifying a triangle by its angle measurement
Right Triangle: A right triangle has one right angle

5. Classifying a triangle by its angle measurement
Acute Triangle: An acute triangle has three acute angles (less than 90°)

6. Classifying a triangle by its angle measurement
Obtuse Triangle: An obtuse triangle has one obtuse angle (more than 90°)

7. Classifying a triangle by its side lengths
Scalene Triangle: A scalene triangle has no congruent sides (all different side lengths)

8. Classifying a triangle by its side lengths
Equilateral Triangle: An equilateral triangle has three congruent sides (all side lengths are the same)

9. Classifying a triangle by its side lengths
Isosceles Triangle: An isosceles triangle has at least two congruent sides

10. Triangle Sum Investigation:

11. Triangle Sum Conjecture
Slides
Triangle Sum Conjecture
The sum of the measures of the angles in EVERY triangle is __________ degrees.
C; m<X + m<Y + m<Z = R: Triangle sum theorem

12. Ex 1 Find x and classify the triangle.53 42 x
x = 85

13. Example 2: Solve for x and classify the triangle.52
(7x + 5) (5x + 3)

14. Example 3: Solve for x and classify the triangle.
(3x – 5) (46 – x)

15. Example 4: Find the measures of the
missing angles. 5 2 60
135 1 3 4

16. Example 5:
Use the diagram to find mMJK.