2/28/17- Arcs, Central Angles, and Inscribed Angles

Circles Day 2 Warm-up

Key idea covered at the end of the warm-up was how the three diagrams at the end just had circles around the angles, making them central angles. We then discussed how we consider “all the way around a circle” to be 360º, and so half-way around a circle is 180º, and if you look at that 3rd diagram on the bottom of the warm-up, the measure of the 180º central angle is equivalent to the measure of the 180º arc. Likewise, the measure of the 90º central angle is equivalent to the measure of the 90º arc. This equivalency only works for central angles and their arcs!


We then practiced on the following yellow WS: 11-Arcs and Central Angles

Key ideas to get through the WS, especially after problem 8:

  • central angle measures equal their intercepted arcs!
  • Be on the lookout for linear pairs, vertical angles, and diameters
  • When you have variables, you need to create and solve an equation
  • Are things equal to each other, or add up to equal something (90? 180? 360?)

After that, we went on to inscribed angles- completing two diagrams on this WS of blank circles: 8 blank circles (We titled it “Angles on Circles”)

We then got practice on the following green WS: 11-Inscribed Angles

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