一块半圆形草坪的周长为128、5m，面积？
\u4e00\u4e2a\u534a\u5706\u5f62\u8349\u576a\u7684\u5468\u957f\u662f128.5m\uff0c\u8fd9\u4e2a\u8349\u576a\u7684\u5360\u5730\u9762\u79ef\u662f\u591a\u5c11\u5e73\u65b9\u7c73\u60a8\u597d\u3002
\u8bbe\u8349\u576a\u534a\u5f84\u4e3ax\u7c73
2x+2x\u00d73.14\u00f72\uff1d128.5
2x+3.14x\uff1d128.5
5.14x\uff1d128.5
x\uff1d25\uff08\u7c73\uff09
\uff0825m\uff09²\u00d73.14\uff1d625m²\u00d73.14\uff1d1962.5m²
\u7b54\uff1a\u8349\u576a\u5360\u5730\u9762\u79ef1962.5\u5e73\u65b9\u7c73
\u795d\u597d\uff0c\u518d\u89c1\u3002
2*3.14*r/2+2r=128.5
(3.14+2)r=128.5
r=25(m)
s=3.14*25*25/2
=981.25(\u5e73\u65b9\u7c73\uff09
\u7b54\uff1a\u8fd9\u4e2a\u8349\u576a\u7684\u5360\u7684\u9762\u79ef\u662f981.25\u5e73\u65b9\u7c73\u3002
πd=257
d=82
绛旓細C=1/2d蟺=128.5 蟺d=257 d=82
绛旓細鍥犱负鍗婂渾鐨勫懆闀=鍦嗗懆闀夸竴鍗+鐩村緞锛屼篃灏辨槸蟺r+2r=128.5鍘樼背锛岃В寰楀崐寰剅=128.5梅5.14=25鍘樼背銆傛墍浠ヨ繖鍧楀湴鐨勯潰绉=蟺r²/2=3.14脳25脳25/2=981.25骞虫柟鍘樼背銆
绛旓細濡傚彸鍥捐蹇冨叕鍥湁涓ゅ潡鍗婂渾褰㈢殑鑽夊潽浠栦滑鐨鍛ㄩ暱閮芥槸128.5绫筹紝杩欎袱鍧楄崏鍧殑鎬婚潰绉槸澶氬皯锛熻В锛氳鍦嗗舰鑽夊潽鐨勭洿寰勬槸d绫筹紝3.14脳d梅2+d=128.5 2.57d=128.5 d=50 闈㈢Н涓猴細3.14脳锛50梅2锛2 =3.14脳625 =1962.5锛堝钩鏂圭背锛夌瓟锛氳繖鍧楄崏鍧殑鎬婚潰绉槸1962.5骞虫柟绫筹紟...
绛旓細涓涓崐鍦嗗舰鑽夊潽鐨勫懆闀挎槸128.5m锛屽嵆:鍗婂緞+鍗婂緞+鍗婂渾寮=128.5 2脳鍗婂緞+(2脳鍗婂緞脳3.14梅2)=128.5,2脳鍗婂緞+鍗婂緞脳3.14=128.5,(2+3.14)脳鍗婂緞=128.5,鍗婂緞=128.5梅5.14=25(m),闈㈢Н=鍗婂緞脳鍗婂緞脳3.14梅2 =25脳25脳3.14梅2 =981.25(骞虫柟绫)...
绛旓細鍗婂渾褰㈢殑鍛ㄩ暱鏈変竴涓潙锛屽畠涓嶆槸鍦嗙殑鍛ㄩ暱鐨勪竴鍗婏紝鑰屾槸鍦嗙殑鍛ㄩ暱鐨勪竴鍗婂姞涓婄洿寰勭殑闀垮害 鍗崇劧鏄袱鍧楀垎绂荤殑鍗婂渾褰㈢殑鑽夊潽锛岄偅涔堝彧闇瑕佹眰涓涓殑鍗婂緞鍗冲彲姹傚嚭闈㈢Н 璁惧崐寰勪负r 蟺r+2r=128.5 5.14r=128.5 r=25(绫)鎬婚潰绉=涓涓暣鍦嗙殑闈㈢Н =蟺r²=3.14脳25²=1962.5(骞虫柟绫)...
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绛旓細璁捐繖鍧鍗婂渾褰㈣崏鍧殑鍗婂緞涓篟锛岀敱棰樻剰寰 2R+1/2*(2鍏R)=128.5 (2+鍏)R=128.5 (2+3.14)R=128.5 5.14R=128.5 瑙ｅ緱R=25(绫)閭ｄ箞锛3.14*25*25 =3.14*625 =1962.5(骞虫柟绫)鎵浠ワ紝杩欎袱鍧鑽夊潽鐨勬婚潰绉负1962.5骞虫柟绫炽
绛旓細鍗婂渾鍛ㄩ暱涓鈭弐+2r=r锛堚垙+2锛夋墍浠锛堚垙+2锛=128.5 绠楀嚭r=5 鎶婁箞鍗婂渾鐨闈㈢Н灏辨槸鈭弐脳r梅2=3.14脳5脳5梅2=39.25
绛旓細杩欎袱鍧鑽夊潽鐨鎬婚潰绉槸1962.5骞虫柟绫炽傚崐寰勶細128.5梅锛3.14+2锛夛紙2蟺r/2+2r=128.5锛宺涓哄崐寰勶級=128.5梅5.14 =25绫 闈㈢Н锛3.14脳25²=3.14脳625 =1962.5骞虫柟绫
绛旓細璁鑽夊潽鍗婂緞涓簒绫 2x+2x脳3.14梅2锛128.5 2x+3.14x锛128.5 5.14x锛128.5 x锛25锛堢背锛夛紙25m锛²脳3.14锛625m²脳3.14锛1962.5m²绛旓細鑽夊潽鍗犲湴闈㈢Н1962.5骞虫柟绫
