An equilateral triangle is also a regular polygon with all angles measuring 60°. A B D C Diagram NOT accurately drawn ABC is an equilateral triangle. Figure 2 Isosceles triangles. Triangles BOD, DOF and BOF are congruent. SUMMARY 1.Two figures are congruent, if they are of the same shape and size. The angles in an equilateral triangle are always 60°. ; Figure 1 Equilateral triangle. Congruent Triangles. Khan Academy is a 501(c)(3) nonprofit organization. In an isosceles triangle, the two equal sides are called legs, and the remaining side is called the base. The types of triangles classified by their sides are the following: . All students, regardless of background or skill level, will have the opportunity to pursue a growth mindset that will allow them to achieve mastery and to demonstrate they can succeed in school, in college, and in their chosen career. 2. According to the types of triangles, the equilateral triangle belongs to the class: «according to its sides» as well as the isosceles triangle and scalene triangle. In geometry, an equilateral triangle is a triangle in which all three sides have the same length. 2.If two sides and the included angle of one triangle is equal to the two sides and the included angle then the two triangles are congruent(by SAS). It is also worth noting that six congruent equilateral triangles can be arranged to form a regular hexagon, making several properties of regular hexagons easily discoverable as well. Equilateral triangle: A triangle with all three sides equal in measure.In Figure 1, the slash marks indicate equal measure. Two triangles are congruent if all six parts have the same measures. Depending on similarities in the measurement of sides, triangles are classified as equilateral, isosceles and scalene. RD Sharma Solutions for Class 9 Mathematics CBSE, 12 Congruent Triangles. We all know that a triangle has three angles, three sides and three vertices. ... Two triangles are said to be similar if the corresponding angles of two triangles are congruent and lengths of … D lies on BC. The three angles and the three sides must match. In some cases, we are allowed to say that two triangles are congruent if a certain 3 parts match because the other 3 MUST be the same because of it. The equilateral triangle: In the equilateral triangle, all the sides are the same length (congruent) and all the angles are the same size (congruent). An isosceles triangle is a triangle that has (at least) two equal side lengths. Isosceles triangle: A triangle in which at least two sides have equal measure (Figure 2). Interior angles are all different. Triangles can be classified according to the lengths of their sides: An equilateral triangle has three sides of the same length. (a) Prove that triangle ADC is congruent to triangle ADB. By lengths of sides. The triangles above have one angle greater than 90°. No excuses. (3) (b) Hence, prove that BD = … A triangle without any congruent sides or angles is called a … Usually, we reserve congruence for two-dimensional figures, but three-dimensional figures, like our chess pieces, can be congruent, too. Hence, they are called obtuse-angled triangle or simply obtuse triangle.. An obtuse-angled triangle can be scalene or isosceles, but never equilateral. We mark the congruent sides by a slash mark. 1) A) scalene B) equilateral C) isosceles 2) A) equilateral B) isosceles C) scalene 3) A) scalene B) isosceles C) equilateral 4) A) scalene B) equilateral C) isosceles 5) Since no triangles are possible, no congruent triangles are possible. Classifying Triangles by Sides and/or Angles Classify each triangle by its sides. To see why this is so, imagine two angles are the same. 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