These lessons will involve the students in investigating and understanding:
• **Theorem 12: Let ABC be a triangle. If a line l is parallel to BC and cuts [AB] in the ratio m: n, then it also cuts [AC] in the same ratio.
Project Maths Theorem 12
• Proof of Theorem 12
Project Maths Theorem 12 (HL
Alison Proof of Theorem 12)
• Conversely, if line a l cuts the sides AB and AC of triangle ABC in the same ratio, then it is parallel to BC.
• The meaning of similar triangles and the difference between similar and congruent triangles.
Similar Triangles - Math Open Reference
Similar Maths is Fun
• **Theorem 13: If two triangles are similar, then their sides are proportional, in order.
Project Maths Theorem 13
• Proof of Theorem 13
Project Maths Theorem 13 (HL)
Alison Proof of Theorem 13
• Conversely, if the sides of two triangles are in proportion, then the two triangles are similar.
Khan