Triangles 3

Similar triangles:
Two triangles are similar if, 

Two angles are same. 

Or, two sides are in equal ratio and one angle is same. 

Or, All sides are in equal ratio.

Properties of two similar triangles: 

 
Ratio of sides = Ratio of heights = Ratio of medians = Ratio of angle bisectors = Ratio of in-radii = Ratio of circumradii.

Ratio of areas = Ratio of squares of corresponding sides.

Congruent triangles:
Two triangles are congruent if,
Three sides are equal.
Or, two sides and one angle are equal. 
Or, two angles and one angle are equal. 
Or, Hypotenuse of a right-angled triangle is equal.