First, students will learn how to use the AA similarity theorem, to find missing side lengths for similar triangles.
Solving similar triangles by Khan Academy
After that, students will see how the theorem can be used to prove that parallel lines always have the same slope.
Proof: parallel lines have the same slope by Khan Academy
Next, students will see how the theorem can be used to prove that perpendicular lines always have negative reciprocal slope.
Proof: perpendicular lines have opposite reciprocal slopes by Khan Academy
After that, students will see how the Pythagorean theorem can be proven using similar triangles.
Pythagoras Theorem: Proof #2: Using 3 similar triangles by Joel Speranza Math
Next, give your students these challenges.
Conclude by giving your students these challenges:
- Overturning Fracsum by NRICH
- Odds and Evens by NRICH
- Only Connect by NRICH
- Maximaze / Minimaze by Pierce School: Problem / Solution