1. 4.1 & 4.2 A Notes

2. Type of ∆DefinitionPicture Equilateral Triangle CLASSIFICATION BY SIDES All sides are 

3. Type of ∆DefinitionPicture Isosceles Triangle CLASSIFICATION BY SIDES At least 2 sides  base leg

4. Type of ∆DefinitionPicture Scalene Triangle CLASSIFICATION BY SIDES No sides are 

5. Type of ∆DefinitionPicture Equiangular Triangle CLASSIFICATION BY ANGLES All angles are 

6. Type of ∆DefinitionPicture Acute Triangle CLASSIFICATION BY ANGLES All angles are acute

7. Type of ∆DefinitionPicture Right Triangle CLASSIFICATION BY ANGLES One right angle leg hypotenuse

8. Type of ∆DefinitionPicture Obtuse Triangle CLASSIFICATION BY ANGLES One obtuse angle and 2 acute angles

9. Interior Angles –Angles inside a shape Exterior Angles –Angles outside a shape Corollary – Statement easily proved from another statement

10. a c b a c b The sum of the measures of a triangle = _______ 180°

11. If two triangles have two angles that are _______, then the third angle is also ___________.   A B CD E F 40° 60° 80°

12. The measure of an exterior angle of a triangle is equal to the sum of the measures of the two remote interior angles. a + b = 180° b + c + d = 180° b + c + d = a + b c + d = a

13. The acute angles of a right triangle are ______________. complementary a c a + c + 90 = 180° a + c = 90°

14. Classify the triangle by its sides and angles. scalene right

15. Classify the triangle by its sides and angles. equilateral equiangular

16. Classify the triangle by its sides and angles. isosceles obtuse

17. 4. Find the value of x. Then classify the triangle by its angles. x + 2x + 90 = 180 3x + 90 = 180 -90 -90 3x = 90 x = 30° 3 30° 60° right

18. 4. Find the value of x. Then classify the triangle by its angles. 2x + 3x + 55 = 180 5x + 55 = 180 -55 -55 5x = 125 x = 25° 5 50° 75° acute

19. 4. Find the value of x. Then classify the triangle by its angles. 180 – 50 – 70 =60° acute 60° 120°

20. 5. Find the measure of each exterior angle shown. x + 80 = 3x – 22 -x -x. 102 = 2x 51° = x 2 80 = 2x – 22 +22 +22 3(51) – 22 =131°

21. 5. Find the measure of each exterior angle shown. 2x + 103 – x = 6x – 7 -x -x. 110 = 5x 22° = x 5 103 = 5x – 7 +7 +7 x + 103 = 6x – 7 6(22) – 7 =125°

22. 6. Solve for the variables. 65° 180 - 90 – 65 = 25°

23. 6. Solve for the variables. 55° 5y + 55 + 70 = 180 5y + 125 = 180 -125 -125 5y = 55 y = 11° 5

24. 6. Solve for the variables. 4x + 2y = 56 5x + y = 34 34° –2 4x + 2y = 56 –10x – 2y = –68 –6x = –12 x = 2 4(2) + 2y = 56 8 + 2y = 56 2y = 48 y = 24

25. 7. Find the measure of each missing angle. 120° 60° 30° 60° 30°