90度园圆心角r20cm的扇形面积怎么算小学数学 在直径是5厘米的圆中画一个圆心角是90度的扇形，并计算扇形的...
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90\u00f7360\u00d73.14\u00d7\uff085\u00d75\uff09+90\u00f7360\u00d73.14\u00d7\uff082\u00d72\uff09-5\u00d72=35.53\u5e73\u65b9\u5398\u7c73
\u6216
\u9634\u5f71\u90e8\u5206\u7684\u9762\u79ef
= (25\u03c0 + 4\u03c0) / 4 - 10
= 29\u03c0 / 4 - 10
= 12.8 \u5e73\u65b9\u5398\u7c73
\u6269\u5c55\u8d44\u6599\uff1a
R\u662f\u6247\u5f62\u534a\u5f84\uff0cn\u662f\u5f27\u6240\u5bf9\u5706\u5fc3\u89d2\u5ea6\u6570\uff0c\u03c0\u662f\u5706\u5468\u7387
\u4e5f\u53ef\u4ee5\u7528\u6247\u5f62\u6240\u5728\u5706\u7684\u9762\u79ef\u9664\u4ee5360\u518d\u4e58\u4ee5\u6247\u5f62\u5706\u5fc3\u89d2\u7684\u89d2\u5ea6
S=n\u03c0R²/360
S=LR/2
\uff08L\u4e3a\u5f27\u957f\uff0cR\u4e3a\u534a\u5f84\uff09
\u53c2\u8003\u8d44\u6599\u6765\u6e90\uff1a\u767e\u5ea6\u767e\u79d1-\u6247\u5f62\u9762\u79ef
\u534a\u5f845cm\u7684\u5706\uff0c\u9762\u79ef\u4e3a3.14\u00d75\u00d75=78.5\uff0c\u5219\u6247\u5f62\u9762\u79ef\u4e3a78.5\u00d7\uff0890/360\uff09=19.625\u5e73\u65b9\u5398\u7c73\u3002
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绛旓細鎵囧舰寮ч暱=20蟺/4 璁惧簳闈㈠崐寰=r 2蟺r=20蟺/4 r=5/2
绛旓細4涓荤殑鍦嗗績瑙鏄90*4=360搴 鍗1涓洯 鍦嗗崐寰勬槸20梅2=10鍘樼背 20脳20-3.14脳10脳10=86 绛旓細鍓╀笅闈㈢Н鏄86骞虫柟鍘樼背
绛旓細涔濆崄搴︾殑寮ч暱鍗犲渾寮ф婚暱鐨勫洓鍒嗕箣涓锛18*18=324*3.1416=1017.878499/4=254.4696248锛岃繖涓節鍗佸害鐨勫渾寮ч暱鏄簩鍗佷簲鐐瑰洓鍥涗竷鍘樼背銆
绛旓細瑙ｈ鎵囧舰鐨勫崐寰勪负r 鐢卞渾鐨勫懆闀2蟺r=12.56 鐭=2 鎵囧舰鐨勯潰绉疭=1/4蟺r^2=3.14骞虫柟鍘樼背
绛旓細鍗婂緞10.71梅锛3.14梅2+2锛=10.71梅3.57 =3鍘樼背 闈㈢Н3.14脳3脳3脳90/360 =28.26脳1/4 =7.065骞虫柟鍘樼背
绛旓細瑙: 璁惧皬鍦嗐佸ぇ鍦嗐鎵囧舰鐨勫崐寰勫垎鍒槸r銆3r銆4r. 鏁翠釜鍟嗘爣鐨勯潰绉槸1/2脳3.14脳(4r)2+1/2脳3.14脳(3r)2=12.5脳3.14脳r2; 闃村奖閮ㄥ垎鐨勯潰绉槸1/2脳3.14脳(3r)2-1/2脳3.14脳r2=4脳3.14脳r2; 鎵浠,闃村奖鍥惧舰闈㈢Н鍗犳暣涓晢鏍囧浘褰㈤潰绉殑4脳3.14脳r2/12.5脳3.14脳r2=32% 鏁...
绛旓細鎵囧舰闈㈢Н=(1/2)*蟺*r^2*(胃/360掳)鍏朵腑锛毾 鏄渾鍛ㄧ巼锛岀害绛変簬3.14159銆俽鏄墖褰㈢殑鍗婂緞锛浳 鏄墖褰㈢殑涓績瑙掞紝鍗曚綅涓哄害鏁般傝繖涓叕寮忕殑鍚箟鏄細鎵囧舰鐨勯潰绉瓑浜庡崐涓渾鐨勯潰绉箻浠ヤ粠璇ュ渾蹇冨埌鎵囧舰杈圭紭鐨勮窛绂伙紙鍗冲崐寰剅锛変笌鍦嗗績瑙搴︽暟锛堝嵆胃锛夌殑姣斿肩殑骞虫柟銆備緥濡傦紝濡傛灉鎴戜滑鏈変竴涓崐寰勪负5鍘樼背鐨勫崐鍦嗗舰鎵囧舰...
绛旓細濡傚浘锛氬皢鍦嗗舰绾哥墖瀵规姌涓ゆ涔嬪悗锛屽緱鍒扮殑鏄竴涓洓鍒嗕箣涓鍦嗐傚渾鐨勭洿寰勬槸6鍘樼背锛屾墍浠ュ渾鐨勫崐寰r=3鍘樼背銆傛墍姹鐨勬墖褰闈㈢Н瀹為檯涓婂氨鏄洓鍒嗕箣涓鍦嗙殑闈㈢Н銆傛暣涓渾鐨勯潰绉疭=蟺r²锛屽洓鍒嗕箣涓鍦嗙殑闈㈢Н锛堜篃灏辨槸鎵姹傜殑鎵囧舰鐨勯潰绉級涓猴細S'=锛1/4锛壪r²=锛1/4锛壝3.14脳3²=7....
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绛旓細鍛ㄩ暱锛1.鍏堟眰鎵囧舰鐨勪袱杈癸紝涔熷彲浠ョ悊瑙ｄ负鏄洿寰勩傚洜涓烘墖褰㈢殑涓よ竟鏄袱鏉″崐寰勩傛墍浠ヤ袱杈圭瓑浜6銆2.姹傚姬绾块暱搴︺傚洜涓烘鎵囧舰鍦嗗績瑙鏄90搴锛岄偅涔堝氨鏄洓鍒嗕箣涓鍦嗐傜瓑浜庝竴涓洿寰勪负6鍘樼背鐨勫渾鐨勫洓鍒嗕箣涓锛屽氨鏄3.14*6/4=4.71鍘樼背銆3.鎶婃墖褰㈢殑涓よ竟鍜屽姬绾垮姞璧锋潵锛6+4.71=10.71銆傞潰绉細鍥犱负姝鎵囧舰鐨勫渾蹇...
