1. 4-1
1.1. dilation: a transformation in which a figure grows larger
1.1.1. isometry: a transformation that never changes with respect to distance.
1.1.1.1. rigid transformation: a transformation that does not change the size or figure of it.
2. 4-2
2.1. acute triangle: a triangle with all 3 angles below 90 degrees.
2.1.1. equiangular triangle:a triangle where all 3 sides are equal.
2.1.1.1. right triangle: a triangle in which one angle is a 90 degree angle.
2.1.1.1.1. obtuse triangle: a triangle in which the angles are above 90 degrees.
3. 4-3
3.1. auxiliary line: a line needed to complete a proof in plane geometry.
3.1.1. corollary: a statement that follows with not little to no proof of an already proven statement.
3.1.1.1. interior: an angle formed formed between parallel lines
3.1.1.1.1. exterior: an angle formed outside of parallel lines.
4. 4-4
4.1. corresponding angles: when 2 lines are crossed by another line.
4.1.1. corresponding sides: 2 angles or 2 sides are congruent if they have the same measure.
4.1.1.1. congruent polygons: have the same number of sides and are corresponding interior angles and sides.
5. 4-5
5.1. triangle rigidity: a property of triangles that states if the side lengths of the triangle are fixed.
5.1.1. included angle: the angle between two sides of a triangle.