如右图,已知等腰直角三角形ABC的面积是12平方厘米,求图色部分的面积 如图所示已知等腰直角三角形ABC面积是12平方厘米求阴影
\u5982\u53f3\u56fe\uff0c\u5df2\u77e5\u76f4\u89d2\u4e09\u89d2\u5f62\u7684\u9762\u79ef\u662f 12 \u5e73\u65b9\u5398\u7c73\uff0c\u6c42\u9634\u5f71\u90e8\u5206\u9762\u79ef\u5982\u53f3\u56fe,\u5df2\u77e5\u5927\u76f4\u89d2\u4e09\u89d2\u5f62\u9762\u79ef\u4e3a12\u5e73\u65b9\u5398\u7c73,\u5219\u9634\u5f71\u90e8\u5206\u7684\u9762\u79ef\u662f\u591a\u5c11?
\u4e09\u89d2\u5f62\u5176\u4e2d\u4e00\u4e2a\u89d2\u662f45\u00b0 \u56e0\u6b64\u8fd9\u4e2a\u4e09\u89d2\u5f62\u662f\u4e2a\u7b49\u8170\u76f4\u89d2\u4e09\u89d2\u5f62.\u8bbe\u4e09\u89d2\u5f62\u7684\u8170\u662fX \u5219X²\u00d71/2=12 X²=24\u53c8X\u662f\u534a\u5706\u7684\u76f4\u5f84 \u534a\u5706\u7684\u9762\u79ef\u662f3.14\u00d7\uff08X/2\uff09²\u00d71/2=9.42\u5e73\u65b9\u5398\u7c73\u800c\u534a\u5706\u4e2d\u7a7a\u767d\u4e09\u89d2\u5f62\u7684\u9762\u79ef\u662f\uff1a1/2\u00d7X\u00d7\uff08X/2\uff09=6\u5e73\u65b9\u5398\u7c73\u6240\u4ee5\u9634\u5f71\u90e8\u5206\u9762\u79ef\u662f9.42-6=3.42\u5e73\u65b9\u5398\u7c73
\u8fc7D\u4f5cBC\u7684\u5782\u7ebf\u4ea4\u70b9\u4e3aE\uff0cDE=1/2AB=r ,2r*2r/2=12 r*r=6
\u53f3\u8fb9\u7684\u9634\u5f71\u9762\u79ef=1/4*\u03c0*r*r-1/2*r*r=3/2\u03c0-3
\u6240\u4ee5\u5168\u90e8\u7684\u9634\u5f71\u4e3a\u53f3\u8fb9\u9634\u5f71\u7684\u4e09\u500d
s=3*\uff083/2\u03c0-3\uff09=3*\uff084.71-3\uff09=5.13
右边的阴影面积=1/4*π*r*r-1/2*r*r=3/2π-3
所以全部的阴影为右边阴影的三倍
s=3*（3/2π-3）=3*（4.71-3）=5.13
12/2=6(cm^2)
π*6/4=3/2π（cm^2）
6-3/2π=1.29（cm^2）
1.29*3=3.87
BC²/2 = 12
BC = 2√6
R = AB = 2√6
r = BC/2 = √6
阴影部分的面积为s 。
s = πr²/2 - (12 - πR²/8)
= 3π + 3π -12
= 6π -12
= 6(π -2)
没有图，特别是涂色部分是哪部分不知道，不好解决的。
绛旓細鈭AB=AC 鈭碅C=PE+PF
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绛旓細鎴戝氨涓嶇敾鍥句簡锛屽仛df鍨傜洿浜ab浜巉锛屸柍abc闈㈢Н涓72锛宔bcd闈㈢Н涓43.2銆傜敱涓夎褰鐩镐技鍘熺悊鐭ラ亾锛宒f闀8锛宐f楂4,鏄撶煡fbdc闈㈢Н涓40,鍒欌柍def闈㈢Н涓 3.2,鍙煡ef闀0.8,鏁卆e闀8-0.8=7.2
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绛旓細1. AC=BC 鈭燗CE+鈭燘CF=90 鈭燗CE+鈭燙AE=90 鈭燘CF+鈭燙BF=90 涓夎褰AEC 涓 涓夎褰FB 鍏ㄧ瓑 鎵浠 EF=AE+BF 2. 鍚屼笂 AEC鍏ㄧ瓑CFB 鎵浠 浠栦滑鐨勭瓑閲忓叧绯讳负 AE=BF+EF
绛旓細杩嘍浣淏C鐨勫瀭绾夸氦鐐逛负E锛孌E=1/2AB=r ,2r*2r/2=12 r*r=6 鍙宠竟鐨勯槾褰遍潰绉=1/4*蟺*r*r-1/2*r*r=3/2蟺-3 鎵浠ュ叏閮ㄧ殑闃村奖涓哄彸杈归槾褰辩殑涓夊 s=3*(3/2蟺-3)=3*(4.71-3)=5.13
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