Proportionality Theorems (Triangle Proportionality, Angle Bisector)
Students will apply the Triangle Proportionality Theorem and the Angle Bisector Theorem to solve for unknown lengths in triangles.
About This Topic
Students will apply the Triangle Proportionality Theorem and the Angle Bisector Theorem to solve for unknown lengths in triangles.
Key Questions
- Explain how the Triangle Proportionality Theorem relates to similar triangles.
- Analyze the conditions under which the Angle Bisector Theorem can be applied.
- Construct a problem that requires the application of both proportionality theorems.
Active Learning Ideas
See all activities→Activities & Teaching Strategies
See all activities
Planning templates for Mathematics
5E Model
The 5E Model structures lessons through five phases (Engage, Explore, Explain, Elaborate, and Evaluate), guiding students from curiosity to deep understanding through inquiry-based learning.
Unit PlannerMath Unit
Plan a multi-week math unit with conceptual coherence: from building number sense and procedural fluency to applying skills in context and developing mathematical reasoning across a connected sequence of lessons.
RubricMath Rubric
Build a math rubric that assesses problem-solving, mathematical reasoning, and communication alongside procedural accuracy, giving students feedback on how they think, not just whether they got the right answer.
More in Similarity and Trigonometry
Dilations and Similarity
Exploring how scale factors affect length and area in proportional figures.
8 methodologies
Proving Triangle Similarity
Students will apply AA, SSS, and SAS similarity postulates to prove triangles are similar.
8 methodologies
Geometric Mean and Right Triangle Similarity
Students will use the geometric mean to solve problems involving altitudes and legs in right triangles.
8 methodologies
Pythagorean Theorem and its Converse
Students will apply the Pythagorean Theorem to find missing side lengths in right triangles and its converse to classify triangles.
8 methodologies
Special Right Triangles (45-45-90 and 30-60-90)
Students will discover and apply the side ratios of 45-45-90 and 30-60-90 triangles.
8 methodologies
Right Triangle Trigonometry
Defining sine, cosine, and tangent as ratios of side lengths in right triangles.
8 methodologies