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Section 1b: Angle Bisector

Directions for Using the Applet:

1. Look at the triangle in the applet. Focus on ∠BAC, the angle at the top. 2. You will see two sliders:
  • The gray slider adjusts the size of the entire angle.
  • The black slider shows how the blue ray divides the angle.
3. Spend a few minutes exploring:
  • Slide both sliders back and forth.
  • Observe how the blue ray interacts with the angle as the sliders move.
4.Use the Point on Object tool (if available) to plot a point F on the blue angle bisector. 5. Use the Angle tool to measure both ∠BAF and ∠CAF.
  • These angles should help you better understand what it means to bisect an angle.
6. If you’re stuck or unsure, scroll to the bottom of the page and watch the “Quick (Silent) Demo.”

Questions to Answer (Write in Complete Sentences):

1. Based on your observations, what does it mean for a ray to bisect an angle? Do not use words like “middle,” “half,” or “down the middle.” Explain clearly in your own words.

2. After measuring ∠BAF and ∠CAF: a. What did you notice about the two angles? b. How does this support your answer to the first question?

Quick (Silent) Demo