Theorem 10.1
If two angles and non-included side of one triangle are congruent to the corresponding angles and non-included side of another triangle, then two triangles are congruent.
Theorem 10.2
If two angles of a triangle are congruent, then the sides opposite to them are also congruent.
Theorem 10.3
In the correspondence of two triangles, if three sides of one triangle are congruent to the corresponding three sides of the other, the two triangles are congruent.
Theorem 10.4
If in the correspondence of two right-angled triangles, the hypotenuse and one side of one are respectively congruent to the hypotenuse and corresponding side of the other, the triangles are congruent.
Theorem 11.1
In a parallelogram: (i) Opposite sides are congruent; (ii) Opposite angles are congruent; (iii) Diagonals bisect each other.
Theorem 11.2
If two sides of a quadrilateral are congruent and parallel, it is a parallelogram.
Theorem 11.3
The line segment joining the midpoints of two sides of a triangle is parallel to the third side and equal to one-half of its length.
Theorem 11.4
The medians of a triangle are concurrent and their point of concurrency is the point of trisection of each median.
Theorem 11.5
If three or more parallel lines make congruent intercepts on a transversal, they also intercept congruent segments on the other line that cuts them.
Theorem 12.1
Any point on the right bisector of a line segment is equidistant from its end points.
Theorem 12.2
Any point equidistant from the end points of a line segment is on the right bisector of it.
Theorem 12.3
The right bisectors of the sides of the triangle are concurrent.
Theorem 12.4
Any point on the bisector of an angle is equidistant from its arms.
Theorem 12.5
Any point inside the angle, equidistant from its arms, is on its bisector.
Theorem 12.6
The bisectors of the angles of the triangle are concurrent.
