● The sum of three angles in a triangle is 180°.
● The exterior angle of a triangle is equal to the sum of the two interior opposite angles.
● The exterior angles of a triangle add up to 360º.
● Two lines segments are congruent if they have the same length.
● Two angles are congruent if the measures of the angles are equal.
● If the corresponding sides and corresponding angles of two plane figures are equal then they are called congruent figures.
● If three sides of one triangle are equal to the corresponding sides of the other triangle then the two triangles are congruent. This is known as Side – Side – Side criterion.
● If two sides and the included angle of a triangle are equal to the corresponding two sides and the included angle of another triangle, then the two triangles are congruent to each other. This is known as Side – Angle – Side criterion.
● If two angles and the included side of one triangle are congruent to the corresponding two angles and the included side of another triangle, then the triangles are congruent This is known Angle-Side-Angle criterion.
● In right angled triangle, the side which is opposite to right angle is the largest side called Hypotenuse.
● If the hypotenuse and one side of a right angled triangle is equal to the hypotenuse and one side of another right angled triangle then the two right angled triangles are congruent. This is known as Right Angle-Hypotenuse Side criterion.
Step-1 : Open the Browser type the URL Link given below (or) Scan the QR Code. GeoGebra work sheet named “Geometry” will open. There are three activities named “Angle sum property”, “Similar triangle” and “Congruence triangle”
Step-2 : 1. In Angle sum Property Drag the vertices A,B and C to change the shape of the triangle and check the Angle sum Property. 2. In the Similar triangles change the shape and move the red triangle by holding Diamond point, over Blue triangle to match each of three angles. 3. In Congruence triangle match the triangles by moving the Blue triangle by dragging P (and rotating using the slider).
Browse in the link
Geometry : https://www.geogebra.org/m/f4w7csup#material/gqagexmx or Scan the QR Code.