负数乘法演示
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①本范例通过动态图形演示负数乘法的几何意义;②涉及核心数学概念包括负数乘法规则、数轴对称、几何变换;③作图要点运用了椭圆(Ellipse)、圆弧(Arc)、平移(Translate)、镜像(Mirror)等GeoGebra命令与对象;④适合初中及以上学生理解乘法运算规律,也可用于微积分初步教学。
GeoGebra 命令及参数
Ellipse((a / 2, sqrt(abs(4 - a^(2) / 4))), (a / 2, (-sqrt(abs(4 - a^(2) / 4)))), 2) → c1Arc(c1, (0, 0), (a, 0)) → left1Arc(c1, (a, 0), (0, 0)) → right1Translate(c1, Vector[(a, 0)]) → c2Translate(c2, Vector[(a, 0)]) → c3Translate(c3, Vector[(a, 0)]) → c4Translate(c4, Vector[(a, 0)]) → c5Arc(c2, ((a * 2), 0), (a, 0)) → right2Arc(c3, ((a * 3), 0), ((a * 2), 0)) → right3Arc(c4, ((a * 4), 0), ((a * 3), 0)) → right4Arc(c5, ((a * 5), 0), ((a * 4), 0)) → right5Arc(c2, (a, 0), ((2 * a), 0)) → left2Arc(c3, ((2 * a), 0), ((3 * a), 0)) → left3Arc(c4, ((3 * a), 0), ((4 * a), 0)) → left4Arc(c5, ((4 * a), 0), ((5 * a), 0)) → left5Mirror(c1, x = 0) → c6Mirror(c2, x = 0) → c7Mirror(c3, x = 0) → c8Translate(c8, Vector[((-a), 0)]) → c9Translate(c9, Vector[((-a), 0)]) → c10Arc(c10, ((-4 * a), 0), ((-5 * a), 0)) → left10Arc(c10, ((-5 * a), 0), ((-4 * a), 0)) → right10Ellipse((a / 2, sqrt(abs(4 - a^(2) / 4))), (a / 2, (-sqrt(abs(4 - a^(2) / 4)))), 4) → cArc(c6, ((-a), 0), (0, 0)) → left6Arc(c7, ((-2 * a), 0), ((-a), 0)) → left7Arc(c8, ((-3 * a), 0), ((-2 * a), 0)) → left8Arc(c9, ((-4 * a), 0), ((-3 * a), 0)) → left9Arc(c6, (0, 0), ((-a), 0)) → right6Arc(c7, ((-a), 0), ((-2 * a), 0)) → right7Arc(c8, ((-2 * a), 0), ((-3 * a), 0)) → right8Arc(c9, ((-3 * a), 0), ((-4 * a), 0)) → right9