~ Module 8 Lesson 2* Notes ~ Classifying Triangles TLW classify triangles by their angle measures and side lengths TLW use triangle classifications to find angle measures and side lengths Triangle Classification – by Angle Measures Acute Triangle Equiangular Triangle Right Triangle Obtuse Triangle ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ TRY THIS! CLASSIFY EACH TRIANGLE BY ANGLE MEASURES. (a) (b) (c) Triangle Classification – by Side Lengths Equilateral Triangle Isosceles Triangle Scalene Triangle ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ TRIANGLE – ON VACATION CLASSIFY THE TRIANGLES BY SIDES. (a) (b) (c) DRAW AN EXAMPLE OF EACH TYPE OF TRIANGLE OR EXPLAIN WHY IF IT IS NOT POSSIBLE. (a) isosceles right (b) equiangular obtuse (c) scalene right (d) equilateral acute (e) scalene equiangular (f) isosceles acute Find the side lengths of the triangles below. (a) (b) y ______ BC = ______ AC = ______ AB = ______ y ______ BC = ______ AC = ______ AB = ______ THE TRIANGLE INEQUALITY THEOREM THE SUM OF THE LENGTHS OF ANY TWO SIDES OF A TRIANGLE IS GREATER THAN THE LENGTH OF THE THIRD SIDE. Decide which of the following sets of side lengths actually form a triangle. (a) 1 cm, 2 cm, 5 cm (d) 5 ft, 7 ft, 12 ft (b) 4 cm, 2 cm, 5 cm (e) 6 yds, 8 yds, 10 yds (c) 3 cm, 2 cm, 5 cm (f) 2 ft, 2 ft, 2 ft Guided Practice Classify each triangle by sides or angles. 1. 2. 3. 4. Find the side lengths of the triangles below. 5. 6. y ______ BC = ______ y ______ BC = ______ AC = ______ AB = ______ AC = ______ AB = ______ The lengths of two sides of a triangle are given. Find the range of possible lengths for the third side. 7. 4 yd., 19 yd. 8. 28 km, 23 km. 9. 9.2 cm, 3.8 cm 10. The lengths of two sides of a triangle are 3 feet and 5 feet. Which could be the length of the third side? (a) 3 feet (b) 8 feet (c) 15 feet (d) 2 feet