Of course, the premise is to know the combination and operation of algebra on similar items.

Three judgments and three properties of parallel lines should be learned well. In the future, it will be proved that parallelogram, or two angles are equal.

Triangles are annoying, and the relationship between angles (one outer angle is equal to the sum of two non-adjacent inner angles ...),

The relationship between sides (used to judge whether a triangle is formed)

The sum of the internal angles of a triangle (the sum of the internal angles of a polygon, which is difficult to remember)

Four hearts (center of gravity, center of gravity, inner heart and outer heart)

Three lines (midline, bisector of inner corner, midline vertical line)

The proof of congruence is very important and difficult.

The probability at this time is not difficult. I remember I still have to learn it in grade three.