如何用尺规作图做已知线段的平行线 尺规作图:过一点做已知直线的平行线怎么做?
\u600e\u4e48\u8fc7\u4e00\u70b9\u505a\u5df2\u77e5\u76f4\u7ebf\u7684\u5e73\u884c\u7ebf\uff1f\uff08\u5c3a\u89c4\u4f5c\u56fe\uff09\u5c3a\u89c4\u505a\u56fe\u5c31\u662f\u53ea\u80fd\u753b\u5706\u548c\u76f4\u7ebf\u3002\u8fc7\u76f4\u7ebf\u5916\u4e00\u70b9\u505a\u5df2\u77e5\u76f4\u7ebf\u7684\u5e73\u884c\u7ebf\u5c3a\u89c4\u505a\u56fe\u97004\u6b65\uff1a1\u3001\u5df2\u76f4\u7ebf\u5916\u7684\u70b9\u4e3a\u5706\u5fc3\uff0c\u505a\u4e0e\u76f4\u7ebf\u6709\u4e24\u4e2a\u4ea4\u70b9\u7684\u5706\uff1b2\u3001\u4ee5\u5176\u4e2d\u4e00\u4e2a\u4ea4\u70b9\u4e3a\u5706\u5fc3\uff0c\u4ee5\u8fd9\u4e2a\u70b9\u4e0e\u76f4\u7ebf\u5916\u7684\u70b9\u7684\u8ddd\u79bb\u4e3a\u534a\u5f84\u505a\u5706\uff0c\u4e0e\u76f4\u7ebf\u76f8\u4ea4\u4e24\u70b9\uff1b3\u3001\u4ee5\u7b2c2\u6b65\u4e2d\u5706\u4e0e\u76f4\u7ebf\u7684\u5176\u4e2d\u4e00\u4e2a\u4ea4\u70b9\u4e3a\u5706\u5fc3\uff0c\u4ee5\u7b2c\u4e8c\u4e2a\u5706\u534a\u5f84\uff08\u8fc7\u7b2c\u4e8c\u4e2a\u5706\u5fc3\uff09\u4e3a\u534a\u5f84\u4f5c\u5706\uff0c\u4e0e\u7b2c\u4e00\u4e2a\u5706\u6709\u4e00\u4e2a\u4ea4\u70b9\uff1b4\u3001\u8fde\u63a5\u7b2c\u4e00\u3001\u4e09\u5706\u7684\u4ea4\u70b9\uff0c\u4e0e\u76f4\u7ebf\u5916\u7684\u70b9\uff0c\u5373\u4e3a\u8981\u6c42\u7684\u5e73\u884c\u7ebf\u3002
1\u3001\u4ee5\u70b9\u4e3a\u5706\u5fc3\uff0c\u753b\u4e00\u4e2a\u8ddf\u76f4\u7ebf\u76f8\u5207\u7684\u5706A\u3002
2\u3001\u4ee5\u5207\u70b9\u4e3a\u5706\u5fc3\uff0c\u753b\u4e00\u4e2a\u540c\u6837\u5927\u5c0f\u7684\u5706B\u3002
3\u3001\u5706B\u8ddf\u76f4\u7ebf\u7684\u4ea4\u70b9\u4efb\u610f\u9009\u4e00\u4e2a\u505a\u5706\u5fc3\uff0c\u753b\u76f8\u540c\u5927\u5c0f\u7684\u5706C\u3002
4\u3001\u753b\u4e00\u6761\u7ecf\u8fc7\u5706A\u7684\u5706\u5fc3\u5e76\u4e0e\u5706C\u76f8\u5207\u7684\u76f4\u7ebf\uff0c\u5373\u662f\u5df2\u77e5\u76f4\u7ebf\u7684\u5e73\u884c\u7ebf\u3002
会有2个交点 连接这2个交点 就画出已知线段的平行线了
先作过一点到已知直线的垂线再作过这点与所作垂线的垂线.
绛旓細鍩烘湰浣滃浘•鍦ㄥ嚑浣曢噷,鎶婇檺瀹氱敤鐩村昂鍜屽渾瑙勬潵鐢诲浘,绉颁负灏鸿浣滃浘.鏈鍩烘湰,鏈甯哥敤鐨勫昂瑙勪綔鍥,閫氬父绉板熀鏈綔鍥.•鍏朵腑,鐩村昂鏄病鏈夊埢搴︾殑;•涓浜涘鏉傜殑灏鸿浣滃浘閮芥槸鐢卞熀鏈綔鍥剧粍鎴愮殑.涓嬮潰浠嬬粛涓ょ鍩烘湰浣滃浘:浣滀竴鏉$嚎娈电瓑浜庡凡鐭ョ嚎娈1銆佷綔涓鏉$嚎娈电瓑浜宸茬煡绾挎鍒╃敤鐩村昂鍜屽渾瑙勫彲浠ヤ綔鍑哄緢澶氬嚑浣曞浘褰...
绛旓細灏鸿浣滃浘杩欐牱鍋氱嚎娈典腑鐐癸細1銆浣滅嚎娈AB锛屽涓嬪浘锛2銆佸垎鍒互A鍜孊涓哄渾蹇冿紝浠ュぇ浜0.5AB闀垮害涓哄崐寰勶紝浣滃渾锛屼氦涓嶤鍜孌锛屽涓嬪浘锛3銆佽繛鎺D锛屼氦AB涓嶦锛孍灏辨槸AB鐨勪腑蹇冿紝濡備笅鍥撅細4銆侀櫎鍘昏緟鍔╃嚎锛孍鐐瑰氨鏄嚎娈礎B鐨勪腑蹇冿紝濡備笅鍥撅細
绛旓細锛1锛夊鍥撅細鈭礎C=BC锛孉D=BD锛屾牴鎹绾挎鍨傜洿骞冲垎绾跨殑鎬ц川鍙煡CD鍗充负AB鐨勫瀭鐩村钩鍒嗙嚎锛涳紙2锛変綔娉曞涓嬶細鈶犱互伪鐨勯《鐐逛负鍦嗗績锛屼换鎰忛暱涓哄崐寰勭敾鍦嗭紝浜の辩殑涓よ竟鍒嗗埆涓篍鈥诧紝F鈥诧紝杩炴帴E鈥睩鈥诧紱鈶′互C涓哄渾蹇冿紝C鈥睩鈥蹭负鍗婂緞鐢诲渾锛屼氦CB浜庣偣E锛屼互E涓哄渾蹇冿紝E鈥睩鈥蹭负鍗婂緞鐢诲渾浜庡墠鍦嗙浉浜や簬鐐笷锛岃繛鎺F锛屽苟...
绛旓細鍏堢敤鐩村昂鐢讳竴鏉$洿绾挎,鍐嶇敤鍦嗚閲忓彇宸茬煡绾挎闀垮害,鍐嶅湪鐢诲嚭鐨勭洿绾挎涓婇噺鍙栫瓑闀跨嚎娈靛嵆鍙
绛旓細浠ョ洿绾垮鐐逛负鍦嗗績,澶т簬鐐瑰埌鐩寸嚎鐨勮窛绂讳负鍗婂緞鐢诲姬銆備氦鐩寸嚎涓ょ偣銆傚啀鍒嗗埆浠ヨ繖涓ょ偣涓哄渾蹇冦傚ぇ浜庤繖涓ょ偣闂磋窛绂荤殑涓鍗婁负鍗婂緞鍦ㄧ洿绾垮彟涓渚х敾寮с備娇涓ゆ潯寮х浉浜ゃ傝繛鎺ョ洿绾垮鐨勭偣鍜岃繖涓氦鐐广傝繖鏉¤繛绾垮氨鏄墍姹傚瀭绾裤傚涓嬪浘鎵绀猴細
绛旓細1.浠鐐逛负鍦嗗績锛屼互宸茬煡绾挎a鐨勯暱搴︿綔涓哄崐寰勭敾寮э紝鐒跺悗杩炴帴鍦嗗績O鍜屾墍鐢诲姬涓婁换鎰忎竴鐐笲锛岀嚎娈礝B涓烘墍姹傘2锛庡凡鐭ョ嚎娈典袱绔偣鍛藉悕涓篈锛孊锛涚劧鍚庤繃A鐐瑰仛涓鏂滃皠绾緼C锛岀劧鍚庡皢绾挎AB娌跨潃灏勭嚎AC骞崇Щ鍒癆鈥橞鈥欙紝A鈥欑偣鍦ㄥ皠绾緼C涓婏紝A鈥橞鈥欎负鎵姹傘
绛旓細鍏堢敤鐩村昂鍒掍竴闀绾挎,璁惧乏杈圭鐐逛负A,1鐢ㄥ渾瑙勫崱绾挎a闀垮害,浠鐐逛负璧风偣鍚戝彸鐢,寰楀彟涓绔偣涓篊;2鐢ㄥ渾瑙勫崱绾挎b闀垮害,浠鐐逛负璧风偣鍚戝彸鐢,寰楀彟涓绔偣涓篋;3鐢ㄥ渾瑙勫崱绾挎b闀垮害,浠鐐逛负璧风偣鍚戝彸鐢,寰楀彟涓绔偣涓篍;4鐢ㄥ渾瑙勫崱绾挎c闀垮害,浠鐐逛负璧风偣鍚戝乏鐢,寰楀彟涓绔偣涓築;鍗崇嚎娈礎B ...
绛旓細濡傚浘鎵绀猴細 锛 绾挎OC=2a-b锛
绛旓細灏鸿浣滃浘杩欐牱鍋氱嚎娈典腑鐐癸細1銆浣滅嚎娈AB锛屽涓嬪浘锛2銆佸垎鍒互A鍜孊涓哄渾蹇冿紝浠ュぇ浜0.5AB闀垮害涓哄崐寰勶紝浣滃渾锛屼氦涓嶤鍜孌锛屽涓嬪浘锛3銆佽繛鎺D锛屼氦AB涓嶦锛孍灏辨槸AB鐨勪腑蹇冿紝濡備笅鍥撅細4銆侀櫎鍘昏緟鍔╃嚎锛孍鐐瑰氨鏄嚎娈礎B鐨勪腑蹇冿紝濡備笅鍥撅細
绛旓細鈭碅M=BM锛孉N=BN銆傚張 鈭礛N=MN锛屸埓鈻矨MN鈮屸柍BMN锛圫SS锛夈傗埓鈭燤AN=鈭燤BN銆 锛1锛夋牴鎹绾挎鍨傜洿骞冲垎绾跨殑鎬ц川浣滃浘銆傦紙2锛夋牴鎹嚎娈靛瀭鐩村钩鍒嗙嚎涓婄殑鐐瑰埌绾挎涓ょ璺濈鐩哥瓑鐨勬ц川锛屽彲寰桝M=BM锛孉N=BN銆侻N鏄叕鍏辫竟锛屼粠鑰孲SS鍙瘉寰椻柍AMN鈮屸柍BMN锛岃繘鑰屽緱鍒扳垹MAN=鈭燤BN鐨勭粨璁恒