Friday, May 6, 2016

Circles, Arc Measure, Arc Length

Last Geometry unit I'm teaching before the MCAS: Circles! Thursday and Friday I taught about measures of central angles and arc measures, and introduced arc lengths. As the unit scheduling turned out, this unit is coming right after Similar Figures, so solving proportions are still fresh in everyone's minds for finding arc length (and soon area of sectors) as fractions of the circumference and area of the whole circle. I'm anticipating that they're going to get a kick out of the different properties of arc measures formed by various angles on circles, like central angles versus inscribed angles.

This is the packet I'm using so far for notes and preliminary practice, from TPT Secondary Math Shop: https://www.teacherspayteachers.com/Product/Circles-Geometry-Circles-Arcs-Arc-Addition-Arc-Lengths-Notes-Assignment-1118676

Word of the Day: "Eyebrow" in Spanish is "ceja". After drawing the symbol over the two endpoints to denote an arc, I realized it looks like an eyebrow over the letters, and went with it. Other bonus, I convinced some of my students to salute anytime they use "Major Arc".