CHAPTER 02 · SEE THE CONNECTION
Similar Triangles.
Move a triangle. Match its corners. Explain why.相似三角形：先動手探索，再配對角同邊，最後學識證明。
Begin at 01 or revisit any idea. Every lesson has a visual exploration, method, worked example, supported questions and takeaways.唔需要先答啱題目。提示、完整解說隨時可以睇。
Concept & correspondence 概念與對應
2 lessonsSame shape, different size
相似三角形的概念
See what stays the same when a triangle is enlarged, reduced or turned.分清楚放大後，邊長會變、角度唔變。
Match vertices and sides
配對對應頂點與邊
Read the order in a similarity statement and match sides even after a triangle turns.跟字母次序配對頂點同邊，唔靠圖形方向估。
Three similarity tests 三種相似條件
3 lessonsEqual angles: AAA
相似條件：三角對應相等
Use angles to establish similarity, with reasons for each angle equality.用角度同原因，逐步證明兩個三角形相似。
Three equal side ratios
相似條件：三邊成比例
Check all three corresponding side ratios and distinguish a valid test from a near miss.核對三對邊嘅比值，識分相似同差少少嘅反例。
Two sides and the included angle
相似條件：兩邊比例與夾角
Recognise the included angle and use the two-side ratio test correctly.認清夾角，將兩邊比例同夾角一齊用。
Proofs & applications 證明與應用
4 lessonsParallel lines: prove, then solve
平行線：先證相似，再求邊長
Write a reasoned AAA proof and distinguish a whole side from one segment.由平行線搵相等角，先證相似，再用完整邊長列比例。
Crossed & overlapping triangles
交叉與重疊三角形
Separate overlapping triangles, match vertices, and justify ratios using angles.分開睇交叉嘅三角形，用相等角配頂點。
A right triangle inside another
直角三角形中的相似證明
Use a shared angle and two right angles to match overlapping triangles.分清楚大小三角形嘅直角位置，配對共用邊嘅角色。
Similar 2-D figures
相似平面圖形、周界與面積
Apply corresponding angles and side ratios to polygons; distinguish length, perimeter and area factors.分清邊長、周界同面積分別用咩倍數。
Connect the three tests and revisit common mistakes.
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