1. Name each polygon and tell whether it appears to be regular or not regular. nonagon, regular; octagon, not regular

2. Learn to classify triangles and solve problems involving angles and side measures of triangles. Triangles and their Classification

3. Classify by sides…. Scalene triangles Isosceles triangles Equilateral triangles ?

4. Triangle Vocab: I scalene triangle isosceles triangle equilateral triangle

5. Marks on the sides of a triangle show which sides have the same measure. No sides are congruent.Two sides are congruent. All sides are congruent.

6. Triangles can be classified by the lengths of their sides. A scalene triangle has no congruent sides. An isosceles triangle has two congruent sides. An equilateral triangle has three congruent sides. Marks on the sides of a triangle show which sides have the same measure. Complete your vocab notes.

7. 10mm 2mm isosceles 5 cm 4 cm 6 cm scalene 4 in 7 in isosceles

8. Classifying Triangles by Lengths of Sides Classify the triangle. The sum of the lengths of the sides is 18 in. c = 6 6 in. N L c M c + (6 + 6) = 18 c + 12 = 18 – 12 =–12 6 in. Side c is 6 inches long. Because LMN has three congruent sides, it is equilateral.

9. Classifying Triangles by Lengths of Sides What kind of triangle is this? The perimeter is 30 cm. 2s = 22 2s + 8 = 30 – 8 = –8 8 cm Now what? If two sides = 22 cm, then one side is... This is an isosceles triangle. 11 cm

10. Classify by angles…. Right triangles Acute triangles Obtuse triangles ?

11. Angle measures??????? acute angle: obtuse angle: right angle: straight angle: Less than 90˚ More than 90 and less than 180 90˚ 180˚

12. A right triangle has one right angle. We have to look at the angles of a triangle to find its classification. An acute triangle has only acute angles An obtuse triangle has one obtuse angle. Acute triangle Right triangle Obtuse triangle

13. Lesson Quiz Classify the triangle as acute, obtuse, or right. 1. 37°, 53°, 90° 2. 60°, 95°, 25° 3. 61°, 78°, 41°4. 115°, 25°, 40° obtuse right acute obtuse

14. Classifying with sides and angles Do we have any congruent sides???? Isosceles What kind of angles do we have? obtuse Do we have any congruent sides???? scalene What kind of angles do we have? right Do we have any congruent sides???? Isosceles What kind of angles do we have? acute

15. What did we do? We classified triangles by their sides and angles. There is much, much more fun stuff that involves triangles and angle measures. Depending on our progress with our required curriculum, maybe we can move on to those topics!