![]() ![]() The measure of the third angle of the given triangle comes out to be 60°. If two angles of a triangle are 60° each, then the triangle is:īy interior angle sum property of triangle, In the right angled isosceles triangle, the center of the circumcircle lies on the hypotenuse and the radius of the circumcircle is half the length of the hypotenuse.Īn isosceles triangle whose two equal sides length is ‘a’ unit and length of its base is ’b’ unit. In the right angled isosceles triangle, the altitude on the hypotenuse is half the length of the hypotenuse. In the right angled isosceles triangle, one angle is a right angle (90 degrees) and the other two angles are both 45 degrees. Two isosceles triangles are always similar. The medians drawn from vertex B and vertex C will not bisect the opposite sides AB and AC. The median drawn from vertex A will bisect BC at right angles. In the above figure, triangle ADB and triangle ADC are congruent right-angled triangles. The altitude from the vertex divides an isosceles triangle into two congruent right-angled triangles. The altitude from vertex A to the base BC is the angle bisector of the vertex angle ∠ A. The altitude from vertex A to the base BC is the perpendicular bisector of the base BC. In the above figure, ∠ B and ∠C are of equal measure. The angles opposite to equal sides are equal in measure. In the above figure, sides AB and AC are of equal length ‘a’ unit. Now, we will discuss the properties of an isosceles triangle.Īn Isosceles Triangle has the Following Properties: Obtuse angled triangle: A triangle whose one interior angle is more than 90 0. Right angled triangle: A triangle whose one interior angle is 90 0. Scalene triangle: A triangle whose all three sides are unequal.Ĭlassification of Triangles on the Basis of their Angles is as FollowsĪcute angled triangle: A triangle whose all interior angles are less than 90 0. Isosceles triangle: A triangle whose two sides are equal. Each of them has their own individual properties.Ĭlassification of Triangles on the Basis of their Sides is as Follows:Įquilateral triangle: A triangle whose all the three sides are equal. The apothem of a regular polygon is also the height of an isosceles triangle formed by the center and a side of the polygon, as shown in the figure below.įor the regular pentagon ABCDE above, the height of isosceles triangle BCG is an apothem of the polygon.Triangles are classified into different types on the basis of their sides and angles. The length of the base, called the hypotenuse of the triangle, is times the length of its leg. When the base angles of an isosceles triangle are 45°, the triangle is a special triangle called a 45°-45°-90° triangle. Base BC reflects onto itself when reflecting across the altitude. Leg AB reflects across altitude AD to leg AC. The altitude of an isosceles triangle is also a line of symmetry. So, ∠B≅∠C, since corresponding parts of congruent triangles are also congruent. Based on this, △ADB≅△ADC by the Side-Side-Side theorem for congruent triangles since BD ≅CD, AB ≅ AC, and AD ≅AD. Using the Pythagorean Theorem where l is the length of the legs. ![]() ABC can be divided into two congruent triangles by drawing line segment AD, which is also the height of triangle ABC. Refer to triangle ABC below.ĪB ≅AC so triangle ABC is isosceles. The base angles of an isosceles triangle are the same in measure. Using the Pythagorean Theorem, we can find that the base, legs, and height of an isosceles triangle have the following relationships: The height of an isosceles triangle is the perpendicular line segment drawn from base of the triangle to the opposing vertex. The angle opposite the base is called the vertex angle, and the angles opposite the legs are called base angles. Parts of an isosceles triangleįor an isosceles triangle with only two congruent sides, the congruent sides are called legs. DE≅DF≅EF, so △DEF is both an isosceles and an equilateral triangle. ![]()
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