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===== Circle Trig =====

(Lecture: 10 minutes)

    * Trig functions are coordinates on unit circle.
    * Angles measure (scaled) arclength.

Based on (ss)[[gsr>book:gsr:ch3|3]] of [[gsr>|the text]], especially
(ss)[[gsr>book:gsr:trig|3.2]].

==== Reflections ====

Having just given students a chance to reflect on the essential ideas of
circle trigonometry (in [[swbq:srsw:rfswtrig|this SWBQ]]),
this is an opportunity to reinforce the geometry of trig with a clear,
unifying lecture.  The order is important: this is circle trig, not (yet)
triangle trig; the trig functions are defined as coordinates on the unit
circle, not as ratios.

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