| 摘要 |
A circular function teaching aid includes a pair of concentrically arranged circles which are relatively movable with respect to each other. One of the circles has visible X and Y axes thereon, while the other circle includes a visible rectangle disposed symmetrically with respect to its center and with the corners of the rectangle being coarcuate. A visible diagonal line connects diametrically opposite corners of the rectangle. A flexible distance selector is attached tangentially to one of the circles.
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