1. This Math Antics video explains the basics of angles and lines.
2. This Math Antics video explains more basics of angles and degrees. What kinds of angles we have: acute, obtuse, reflex, straight, etc. Also complementary and supplementary angles
3. This Khan Academy video explains more basics of angles. How to label angles, and what are lines, rays, and line segments.
4. This Khan Academy video explains more basics of angles. Adjacent angles, complementary angles, supplementary angles.
5. Here is another video that explains supplementary and complementary angles
6. This Khan Academy video explains more types of angles: corresponding angles, alternate exterior angles, and transversals.
7. This Math Antics video explains all about triangles: different types and properties of the different types, and also interior and exterior angles
8. This Math Antics video explains all about quadrilaterals: different types (square, rectangle, rhombus, parallelogram, trapezoid), and properties of the different types, and also interior and exterior angles.
9. This Khan Academy video explains the relationships between angles inside polygons and outside polygons.
10. This Khan Academy video explains the relationships between exterior angles on a polygon.
11. This Khan Academy video explains medians, midpoints, and centroids of triangles.
12. This video also explains properties of right bisectors (perpendicular bisectors).
13. This Khan Academy video reviews the basic properties of right bisectors (perpendicular bisectors), medians, midpoints, and centroids.
14. This video explains medians and altitudes, and also has some practise problems so you can practise using them
15. This Khan Academy video proves that the diagonals in a parallelogram bisect each other. That is, when you draw the diagonals across each other, they will split each other into exactly equal halves. This is a more challenging video - I suggest you DRAW a parallelogram during the video and follow him during the explanation.
16. This Khan Academy video proves that opposite sides of a parallelogram are congruent. That is, when you draw a diagonal across the parallelogram, both triangles will be congruent (exactly the same shape and size). This is a more challenging video - I suggest you DRAW a parallelogram during the video and follow him during the explanation.