Appliquer le théorème de Thalès (1) - Troisième
Yvan Monka・8 minutes read
The video explains how to calculate lengths using Talès' theorem for triangles BPR and BCD, establishing a proportionality relation between sides and using the cross product rule to find the missing length BR as 10/3 or approximately 3.3. It provides further exercises to practice the application of the theorem.
Insights
- Talès' theorem is a mathematical tool used to find unknown lengths in triangles by establishing proportional relationships between corresponding sides of similar triangles.
- The video tutorial provides a step-by-step demonstration of applying Talès' theorem to determine the missing length BR in a configuration involving parallel lines and multiple triangles, offering viewers a practical example to understand the concept better.
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Recent questions
How can I calculate lengths using Talès' theorem?
By applying Talès' theorem to triangles with given lengths and parallel lines, you can establish a proportionality relation between sides to calculate missing lengths.
What is the configuration for applying Talès' theorem?
The configuration involves multiple triangles with given lengths and parallel lines, ensuring specific points lie on certain lines and segments are parallel.
What does Talès' theorem establish between triangles?
Talès' theorem establishes a proportionality relation between sides of two triangles, allowing for the calculation of missing lengths based on known values.
How is the formula set up when using Talès' theorem?
The formula sets up the sides of the small triangle at the top and the sides of the large triangle at the bottom, facilitating the calculation of missing lengths through proportionality.
What method is used to calculate missing lengths with Talès' theorem?
By utilizing the cross product rule, you can calculate missing lengths in triangles, as demonstrated in the video where the length BR is determined to be 10/3 or approximately 3.3.
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Summary
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Calculating Lengths with Talès' Theorem
- The video teaches how to calculate a length using Talès' theorem and provides a link for further exercises.
- The configuration involves multiple triangles with given lengths and parallel lines.
- Talès' theorem is applied to triangles BPR and BCD, ensuring P is on BC, R is on BD, and PR is parallel to CD.
- The theorem establishes a proportionality relation between sides of the two triangles.
- The formula is set up with sides of the small triangle at the top and sides of the large triangle at the bottom.
- Using the cross product rule, the missing length BR is calculated as 10/3 or approximately 3.3.
