Published on November 5, 2007
4-1 Classifying Triangles: 4-1 Classifying Triangles Pg. 180-187 By Kara Stilson Slide2: vertices- sides that intersect only at their endpoints polygon- a closed figure in a plane that is made up of segments sides- segments that make a closed figure in a plane triangle- three-sided polygon Slide3: scalene triangle- a triangle with no congruent sides isosceles triangle- a triangle with at least two congruent sides equilateral triangle- a triangle with all congruent sides equiangular triangle- an acute triangle in which all angles are congruent Slide4: Vertex angle- the angle formed by the congruent sides Legs- the congruent sides of a triangle Base angles- the two angles formed by the base and one of the congruent sides Base- the side opposite of the vertex acute angle- less than 90 degrees right angle- exactly 90 degrees obtuse angle- bigger than 90 degrees and less than 180 Slide5: A B E C D Classify <ABC, <BCD, and < BCE as acute, obtuse, right, or equiangular. #1... <ABC appears to be an equiangular triangle. <BCD appears to be a right triangle. <BCE appears to be an obtuse triangle. Slide6: #2 Triangle RST is an isosceles triangle. <R is the vertex angle, RS= x +7, ST= x-1, and RT= 3x-5. Find x, RS, ST, and RT. x+7 R S T x-1 3x-5 If x=6, then RS=6+7 or 13. Since RS=RT, RT =13. Since ST=x-1, ST= 6-1 or 5. The legs of the isosceles triangle are each 13 units long and the base is 5 units long. RS=RT x+7=3x-5 12=2xn 6=x Since <R is the vertex angle, the side opposite <R=ST, is the base of the triangle. The congruent legs are RS and RT. So, RS=RT. Slide7: #3 Given < DAR with vertices D(2,6), A(4,-5),and R(-3,0), use the distance formula to show that <DAR is scalene. USE THE DISTANCE FORMULA! x y DR= = AD = = = 125 = 61 RA= = = 74 Since no two sides have the same length, the triangle is scalene. R=(-3,0) D=(2,6) A=(4,5) Slide8: Pg. 184- 187 All…. 51-62 Odds….. 17-43 Happy Halloween!