多边形外角 by Heather Pierce
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①本范例演示多边形外角的性质与计算;②涉及核心概念包括外角和定理、多边形内角与外角关系;③构造要点:使用 GeoGebra 命令如 Dilate(缩放)、Ray(射线)、Segment(线段)、Min(最小值)、Circle(圆)、Intersect(交点)、CircleSector(扇形)、Vector(向量)、Translate(平移);对象包括 TC, J, d, TC', TB, TB', TA, TA', tf, tg, th, ti, tj, tk, ta, tc, te, tp, TD, TE, TF, TG, TH, TI, tsec1, tsec2, tu, tsec3, tsec1', tv, tsec2', tw, tsec3', triangle(三角形)、quadrilateral(四边形)、pentagon(五边形)、hexagon(六边形)、button1(按钮)、QA、QB;④适合初中及以上学生学习多边形几何性质,或用于数学教学演示。
GeoGebra 命令及参数
Dilate(TC, If[0 < d ≤ 1, 1 - d, 0], J) → TC'Dilate(TB, If[0 < d ≤ 1, 1 - d, 0], J) → TB'Dilate(TA, If[0 < d ≤ 1, 1 - d, 0], J) → TA'Ray(TA, TB) → tfRay(TB, TC) → tgRay(TC, TA) → thSegment(TA, TB) → tiSegment(TB, TC) → tjSegment(TC, TA) → tkMin({ti, tj, tk}) → taCircle(TA, (0.15 * ta)) → tcCircle(TB, (0.15 * ta)) → teCircle(TC, (0.15 * ta)) → tpIntersect(tc, th, 2) → TDIntersect(tc, tf) → TE,Intersect(tp, tg, 2) → TFIntersect(tp, th) → TG,Intersect(te, tf, 2) → THIntersect(te, tg) → TI,CircleSector(TA, TD, TE) → tsec1CircleSector(TB, TH, TI) → tsec2Vector(TA, TA') → tuCircleSector(TC, TF, TG) → tsec3Translate(tsec1, tu) → tsec1'Vector(TB, TB') → tvTranslate(tsec2, tv) → tsec2'Vector(TC, TC') → twTranslate(tsec3, tw) → tsec3'Segment(QA, QB) → qfSegment(QB, QC) → qgSegment(QC, QD) → qhSegment(QD, QA) → qiMin({qf, qg, qh, qi}) → qaCircle(QA, (0.15 * qa)) → qcCircle(QB, (0.15 * qa)) → qeCircle(QC, (0.15 * qa)) → qkCircle(QD, (0.15 * qa)) → qpRay(QA, QB) → qjRay(QB, QC) → qlRay(QC, QD) → qmRay(QD, QA) → qnIntersect(qc, qn, 2) → QEIntersect(qc, qf) → QF,Intersect(qe, ql) → QG,Intersect(qe, qj, 2) → QHIntersect(qk, ql, 2) → QIIntersect(qk, qm) → QK,Intersect(qp, qm, 2) → QLIntersect(qp, qi) → QM,CircleSector(QA, QF, QE) → qsec1CircleSector(QB, QG, QH) → qsec2CircleSector(QC, QK, QI) → qsec3CircleSector(QD, QM, QL) → qsec4Dilate(QA, If[0 < d ≤ 1, 1 - d, 0], J) → QA'Dilate(QB, If[0 < d ≤ 1, 1 - d, 0], J) → QB'Dilate(QC, If[0 < d ≤ 1, 1 - d, 0], J) → QC'Dilate(QD, If[0 < d ≤ 1, 1 - d, 0], J) → QD'Vector(QA, QA') → quVector(QB, QB') → qvVector(QC, QC') → qwVector(QD, QD') → qbTranslate(qsec4, qb) → qsec4'Translate(qsec1, qu) → qsec1'Translate(qsec2, qv) → qsec2'Translate(qsec3, qw) → qsec3'Segment(PA, PB) → pfSegment(PB, PC) → pgSegment(PC, PD) → phSegment(PD, PE) → p_iSegment(PE, PA) → pjMin({pf, pg, ph, p_i, pj}) → paCircle(PA, (0.2 * pa)) → pcCircle(PB, (0.2 * pa)) → peCircle(PC, (0.2 * pa)) → pkCircle(PD, (0.2 * pa)) → ppCircle(PE, (0.2 * pa)) → pqIntersect(pc, pf) → PF,Intersect(pe, pg) → PG,Intersect(pk, ph) → PH,Intersect(pp, p_i) → PI,Intersect(pq, pj) → PK,Ray(PE, PA) → plRay(PA, PB) → pmRay(PB, PC) → pnRay(PC, PD) → prRay(PD, PE) → psIntersect(pc, pl, 2) → PLIntersect(pe, pm, 2) → PMIntersect(pk, pn, 2) → PNIntersect(pp, pr, 2) → POIntersect(pq, ps, 2) → PPCircleSector(PA, PF, PL) → psec5CircleSector(PB, PG, PM) → psec1CircleSector(PC, PH, PN) → psec2CircleSector(PD, PI, PO) → psec3CircleSector(PE, PK, PP) → psec4Dilate(PA, If[0 < d ≤ 1, 1 - d, 0], J) → PA'Dilate(PB, If[0 < d ≤ 1, 1 - d, 0], J) → PB'Dilate(PC, If[0 < d ≤ 1, 1 - d, 0], J) → PC'Dilate(PD, If[0 < d ≤ 1, 1 - d, 0], J) → PD'Dilate(PE, If[0 < d ≤ 1, 1 - d, 0], J) → PE'Vector(PA, PA') → puTranslate(psec5, pu) → psec5'Vector(PB, PB') → pvTranslate(psec1, pv) → psec1'Vector(PC, PC') → pwTranslate(psec2, pw) → psec2'Vector(PD, PD') → pbTranslate(psec3, pb) → psec3'Vector(PE, PE') → pu_1Translate(psec4, pu_1) → psec4'Segment(HA, HB) → hfSegment(HB, HC) → hgSegment(HC, HD) → hhSegment(HD, HE) → hiSegment(HE, HF) → hjSegment(HF, HA) → hkMin({hf, hg, hh, hi, hj, hk}) → aCircle(HA, (0.2 * a)) → hcCircle(HB, (0.2 * a)) → heCircle(HC, (0.2 * a)) → hpCircle(HD, (0.2 * a)) → hqCircle(HE, (0.2 * a)) → hrCircle(HF, (0.2 * a)) → hsIntersect(hc, hf) → HG,Intersect(he, hg) → HH,Intersect(hp, hh) → HI,Intersect(hq, hi) → HK,Intersect(hr, hj) → HL,Intersect(hs, hk) → HM,Ray(HA, HB) → hlRay(HB, HC) → hmRay(HC, HD) → hnRay(HD, HE) → htRay(HE, HF) → hbRay(HM, HA) → hf_1Intersect(hc, hf_1, 2) → HNIntersect(he, hl, 2) → HOIntersect(hp, hm, 2) → HPIntersect(hq, hn, 2) → HQIntersect(hr, ht, 2) → HRIntersect(hs, hb, 2) → HSCircleSector(HA, HG, HN) → hsec1CircleSector(HB, HH, HO) → hsec2CircleSector(HC, HI, HP) → hsec3CircleSector(HD, HK, HQ) → hsec4CircleSector(HE, HL, HR) → hsec5CircleSector(HF, HM, HS) → hsec6Dilate(HA, If[0 < d ≤ 1, 1 - d, 0], J) → HA'Dilate(HB, If[0 < d ≤ 1, 1 - d, 0], J) → HB'Dilate(HC, If[0 < d ≤ 1, 1 - d, 0], J) → HC'Dilate(HD, If[0 < d ≤ 1, 1 - d, 0], J) → HD'Dilate(HE, If[0 < d ≤ 1, 1 - d, 0], J) → HE'Dilate(HF, If[0 < d ≤ 1, 1 - d, 0], J) → HF'Vector(HA, HA') → uTranslate(hsec1, u) → hsec1'Vector(HB, HB') → vTranslate(hsec2, v) → hsec2'Vector(HC, HC') → wTranslate(hsec3, w) → hsec3'Vector(HD, HD') → bTranslate(hsec4, b) → hsec4'Vector(HE, HE') → cTranslate(hsec5, c) → hsec5'Vector(HF, HF') → eTranslate(hsec6, e) → hsec6'