Looking Back

(1) objects are objects having the same shape and size.

(2) The method of superimposition examines the of plane figures.

(3) Two line segments say, AB and CD are congruent if they have lengths. We write this as AB ≅ CD. However, it is common to write it as AB = CD.

(4) If all the parts of one triangle are equal to the corresponding parts of other triangle, then the triangles are .

(5) The necessary and sufficient conditions for two triangles to be congruent are as follows:

(i) Side-Side-Side (SSS) criterion for congruence: If three sides of a triangle are equal to the corresponding three of another triangle, then the triangles are congruent.

(ii) Side-Angle-Side(SAS) criterion for congruence: If two sides and the angle between the two sides of a triangle are equal to the corresponding two sides and the angle of another triangle, then the triangles are congruent.

(iii) Angle-Side-Angle criterion of congruence: If two angles and the included of a triangle are equal to the corresponding two angles and included of another triangle then the triangles are congruent.

(iv) Right-Angle Hypotenuse criterion of congruence: If the hypotenuse and one side of a right-angled triangle are to the corresponding hypotenuse and side of the other right-angled triangle, then the triangles are congruent.