王阿姨用25.7米长的篱笆围了一块半圆形的菜地,这块菜地的面积是多少平方米 王林的爸爸用长25.7米的篱笆,围成了一块半圆形的菜地,这块...
\u7528120\u7c73\u957f\u7684\u7bf1\u7b06\u56f4\u4e00\u5757\u83dc\u5730\u8fd9\u5757\u83dc\u5730\u5bbd\u662f20\u7c73\u8fd9\u5757\u83dc\u5730\u957f\u591a\u5c11\u7c73\uff1f\u9762\u79ef\u591a\u5c11\u83dc\u5730\uff1f\u957f=120/2-20=40\u7c73\u3002
\u957f\u65b9\u5f62\u7684\u9762\u79ef=\u957f*\u5bbd=40*20=800\u5e73\u65b9\u7c73\u3002
\u8003\u70b9\uff1a\u957f\u65b9\u5f62\u3001\u6b63\u65b9\u5f62\u7684\u9762\u79ef\u3002
\u89e3\u9898\u65b9\u6cd5\uff1a\u6c42\u51fa\u957f\u65b9\u5f62\u83dc\u5730\u7684\u5bbd\uff0c\u518d\u6839\u636e\u957f\u65b9\u5f62\u7684\u9762\u79ef\u516c\u5f0f\u8fdb\u884c\u89e3\u7b54\u3002
\u6269\u5c55\u8d44\u6599\uff1a
\u76f8\u4f3c\u4f8b\u9898\uff1a
1\u3001\u6709\u4e00\u5757\u957f\u65b9\u5f62\u83dc\u5730\uff0c\u5b83\u8f83\u957f\u7684\u4e00\u6761\u8fb9\u9760\u7740\u5899\uff0c\u957f20\u7c73\uff0c\u7528\u7bf1\u7b06\u5c06\u8fd9\u4e2a\u83dc\u5730\u56f4\u8d77\u6765\u898140\u7c73\uff0e\u8fd9\u4e2a\u83dc\u5730\u7684\u9762\u79ef\u662f\u591a\u5c11\uff1f
\u5bbd\uff1a\uff0840-20\uff09\u00f72=20\u00f72=10\uff08\u7c73\uff09
\u9762\u79ef\uff1a20\u00d710=200\uff08\u5e73\u65b9\u7c73\uff09
2\u3001\u7237\u7237\u7528120\u7c73\u957f\u7684\u7bf1\u7b06\u56f4\u4e86\u4e00\u4e2a\u957f\u4e0e\u5bbd\u7684\u6bd43:2\u7684\u957f\u65b9\u5f62\u83dc\u5730,\u8fd9\u5757\u83dc\u5730\u7684\u9762\u79ef\u662f\u591a\u5c11?
\u957f\uff1a120\u00f72x3/\uff083+2\uff09=36\uff08\u7c73\uff09
\u5bbd\uff1a120\u00f72x2/\uff083+2\uff09=24\uff08\u7c73\uff09
\u9762\u79ef=\u957fx\u5bbd=36x24=864\uff08\u5e73\u65b9\u7c73\uff09
3\u3001\u7528120\u7c73\u957f\u7684\u7bf1\u7b06\u56f4\u6210\u4e00\u5757\u957f\u65b9\u5f62\u83dc\u5730,\u8981\u4f7f\u83dc\u5730\u7684\u957f\u662f\u5bbd\u76842\u500d,\u90a3\u4e48\u83dc\u5730\u7684\u957f\u548c\u5bbd\u5404\u662f\u591a\u5c11\uff1f
120/2=60\u7c73\uff0c60/(2+1)=20\u7c73\uff0c20*2=40\u7c73
\u6240\u4ee5\u957f40\u7c73\uff0c\u5bbd20\u7c73\u3002
\u89e3\u7b54\uff1a
\u6839\u636e\u5706\u5468\u957f\u516c\u5f0f
\u5706\u5468\u957f=2\u03c0 r
\u534a\u5706\u5f62\u5468\u957f\u4e3a
\u03c0 r=25.7
r=25.7/\u03c0
\u5706\u9762\u79ef\u4e3a\u03c0 r2
\u534a\u5706\u9762\u79ef\u4e3a\u03c0 r2/2= \u03c0 *\uff0825.7/ \u03c0 \uff092/2 \uff08\u03c0=3.14\uff09
=105 \u5e73\u65b9\u7c73
\u6240\u4ee5\u8fd9\u5757\u5730\u7684\u9762\u79ef\u662f105\u591a\u5c11\u5e73\u65b9\u7c73\u3002
这块菜地的面积是
5x5x3.14/2=39.25平方米
绛旓細楦″満鍗婂緞锛25.7梅(3.14+2)=5绫 楦″満闈㈢Н锛3.14脳5²梅2=39.25绫²绛旓細杩欎釜鍏婚浮闈㈢Н鏄39.25绫²銆
绛旓細璁惧崐寰勪负r,渚濋鎰 蟺r+2r=25.7,鎵浠=25.7/(蟺+2)鈮5锛屾墍浠ュ崐鍦嗛潰绉=锛埾/2锛塺^2=12.5蟺鈮39.3骞虫柟绫.
绛旓細25.7梅锛3.14+2锛夛紳5 5x5x3.14梅2
绛旓細25*3.14/2=39.25
绛旓細鐩村緞 25.7/(1.57+1)=10 闈㈢Н 3.14x5x5/2=39.25骞崇背
绛旓細鍥犱负鏄崐鍦嗚姳鍦冿紝鎵浠ュ懆闀=鍗婂渾+鐩村緞=蟺r+2r=25.7绫銆傛墍浠ヨ姳鍦冨崐寰=25.7梅锛3.14+2锛=25.7梅5.14=5绫筹紝鎵浠ヨ姳鍦冮潰绉槸蟺r²/2=3.14脳5脳5/2=39.25骞虫柟绫炽
绛旓細鍗婂渾鍛ㄩ暱蟺 r=25.7绠楀嚭鍗婂緞r 鍐嶇敤闈㈢Н鍏紡蟺 r²闄や互2灏辨槸瀹冪殑闈㈢Н浜
绛旓細25.7梅(3.14+2)=5绫筹紙鍘熸潵鐨勫崐寰勶級5+2梅2=6绫筹紙澧炲姞鍚庣殑鍗婂緞锛3.14脳锛6^2-5^2)梅2 =3.14脳11梅2 =17.27骞虫柟绫 绛旓細闈㈢Н澧炲姞浜17.27骞虫柟绫炽
绛旓細銆愶紙25.7梅3.14锛壝2銆²脳3.14=105.17锛坢²锛夋垜鐨勬瘮杈冪畝鍗曪紝浣犵洿鎺ユ妱涓婂幓灏卞彲浠ワ紝閲囩撼鎴戞妸銆
绛旓細妤间笂鐨勪袱浣嶆妸鍗婂渾鐨勫懆闀挎悶閿欎簡:鍗婂渾鐨勫懆闀跨敱涓鏉$洿寰+鍦嗙殑鍛ㄩ暱鐨勪竴鍗婄粍鎴 涓鏉$洿寰=2鏉″崐寰 2r+3.14r=25.7 r(2+3.14)=25.7 r5.14=25.7 r=5 闈㈢Н鏄:5脳5脳3.14梅2=39.25骞虫柟鍘樼背