Symilarity

Two geometrical objects are called similar if one is congruent to the result of a uniform scaling (enlarging or shrinking) of the other. One can be obtained from the other by uniformly "stretching", possibly with additional rotation, i.e., both have the same shape, or additionally the mirror image is taken, i.e., one has the same shape as the mirror image of the other. For example, all circles are similar to each other, all squares are similar to each other, and all parabolas are similar to each other. On the other hand, ellipses are not all similar to each other, nor are hyperbolas all similar to each other. Two triangles are similar if and only if they have the same three angles, the so-called "AAA" condition. However, since the sum of the interior angles in a triangle is fixed in an euclidean plane, as long as two angles are the same, all three are, called "AA

Type of Triangle 2

Triangles can also be classified according to their internal angles, described below using degrees of arc:
[1] A right triangle (or right-angled triangle, formerly called a rectangled triangle) has one 90° internal angle (a right angle). The side opposite to the right angle is the hypotenuse; it is the longest side in the right triangle. The other two sides are the legs or catheti (singular: cathetus) of the triangle.
[2] An oblique triangle has no internal angle equal to 90°.
[3] An obtuse triangle is an oblique triangle with one internal angle larger than 90° (an obtuse angle).

An acute triangle is an oblique triangle with internal angles all smaller than 90° (three acute angles). An equilateral triangle is an acute triangle, but not all acute triangles are equilateral triangles

Type of Triangel 1

Triangles can be classified according to the relative lengths of their sides:
[1] In an equilateral triangle, all sides are of equal length. An equilateral triangle is also an equiangular polygon, i.e. all its internal angles are equal—namely, 60°; it is a regular polygon.
[2] In an isosceles triangle, two sides are of equal length (originally and conventionally limited to exactly two). An isosceles triangle also has two equal angles: the angles opposite the two equal sides.
[3] In a scalene triangle, all sides have different lengths. The internal angles in a scalene triangle are all different.