将圆心角120度，半径为3的扇形作为圆锥的侧面，求圆锥的表面积 直接 写答案!
\u5c06\u5706\u5fc3\u89d2120\u5ea6\uff0c\u534a\u5f84\u4e3a3\u7684\u6247\u5f62\u4f5c\u4e3a\u5706\u9525\u7684\u4fa7\u9762\uff0c\u6c42\u5706\u9525\u7684\u8868\u9762\u79ef \u76f4\u63a5 \u5199\u7b54\u6848!\u89e3\uff1a\u5706\u9525\u7684\u4fa7\u9762\u79ef\u7b49\u4e8e\uff1a\u03c0\u00d73²\u00d7120/360=3\u03c0
\u5706\u9525\u7684\u5e95\u9762\u79ef\u7b49\u4e8e\uff1a\u03c0\u00d7\uff082\u00d7\u03c0\u00d73\u00d7120/360\u00f72\u03c0\uff09²=\u03c0
\u5706\u9525\u7684\u8868\u9762\u79ef\u7b49\u4e8e\uff1a3\u03c0+\u03c0=4\u03c0\u224812.56
\u89e3\uff1a
\u8bbe\u5706\u9525\u6bcd\u7ebf\u4e3aL,\u5219\uff1a 3\u03c0=1/3\uff08\u03c0L^2),\u5f97L=3.
\u8bbe\u5706\u9525\u5e95\u9762\u534a\u5f84\u4e3aR\uff0c\u5219\uff1a1/3(2\u03c0L)=2\u03c0R,\u5f97R=1.
\u5706\u9525\u7684\u5e95\u9762\u79ef\uff1a\u03c0R^2=\u03c0
\u5706\u9525\u7684\u8868\u9762\u79ef\uff1a3\u03c0 + \u03c0 =4\u03c0
\u5706\u9525\u7684\u9ad8\uff1ah=\u221a L^2 -R^2 =\u221a 9-1 =2\u221a2
\u5706\u9525\u7684\u4f53\u79ef\uff1a1/3\uff08\u03c0R^2h)=(2\u221a2)\u03c0/3
圆锥的底面积等于：π×（2×π×3×120/360÷2π）²=π
圆锥的表面积等于：3π+π=4π≈12.56
nπR²/360=120×π×3
=π
≈3.14
4pai,爪机没这个符号
绛旓細宸茬煡鎵囧舰鐨勫渾蹇冭涓120搴锛屽崐寰勪负3鍘樼背锛屽垯杩欎釜鎵囧舰鐨勯潰绉槸3蟺骞虫柟鍘樼背銆傛牴鎹鎰忓彲鐭ワ細n=120搴︼紝r=3鍘樼背 S鎵囧舰=n蟺r^2/360 鎵浠鎵囧舰=120*蟺3^2/360=3蟺骞虫柟鍘樼背 鍥犳杩欎釜鎵囧舰鐨勯潰绉槸3蟺骞虫柟鍘樼背
绛旓細銆愯В绛斻慡鎵囧舰 =120脳蟺脳3²梅360 =9蟺梅3 =3蟺 =9.42骞虫柟绫 鏁呮墖褰㈢殑闈㈢Н鏄9.42骞虫柟绫 銆愮偣璇勩戞墖褰㈢殑闈㈢Н鍏紡鏄疭= n蟺r²/360,鍏朵腑 n鏄墖褰鍦嗗績瑙掞紝r鏄墖褰㈢殑鍗婂緞锛s鏄墖褰㈢殑闈㈢Н銆
绛旓細瑙ｏ細鍦嗛敟鐨勪晶闈㈢Н绛変簬锛毾脳3²脳120/360=3蟺 鍦嗛敟鐨勫簳闈㈢Н绛変簬锛毾脳锛2脳蟺脳3脳120/360梅2蟺锛²=蟺 鍦嗛敟鐨勮〃闈㈢Н绛変簬锛3蟺+蟺=4蟺鈮12.56
绛旓細鍦ㄤ竴涓鍗婂緞涓3cm鐨勫渾涓,鐢讳竴涓鍦嗗績瑙掍负120搴︾殑鎵囧舰,杩欎釜鎵囧舰鐨勯潰绉=1/3脳鍦嗙殑闈㈢Н =1/3脳3.14脳3脳3 =9.42骞虫柟鍘樼背锛
绛旓細棣栧厛姹傚嚭鎵囧舰鐨勬墍鍦ㄥ渾鐨勫懆闀匡細C=2蟺r 鎵囧舰寮ч暱鍗犺鍦嗙殑锛120/360,鍗1/3;鎵浠ユ墖褰㈠姬闀匡細L=(1/3)脳2蟺r=2蟺r/3=2蟺=6.28cm 锛堝叾涓璻涓鍗婂緞3cm,蟺涓3.14)
绛旓細宸茬煡鎵囧舰鐨鍗婂緞涓R=3cm锛鍦嗗績瑙涓篈=120搴︼紝鎵囧舰鐨勯潰绉负Scm骞虫柟锛堢粨鏋滀繚鐣檖ai)S=PI*R^2*A/360 =PI*3^2*120/360 =PI*9/3 =3*PI骞虫柟鍘樼背
绛旓細鍗婂緞涓3鐨鍦嗗叾鍛ㄩ暱锛3*2*3.14锛120搴鐨鍦嗗績瑙鎵瀵圭殑寮ч暱涓哄渾鍛ㄩ暱鐨1/3,鎵浠ユ槸2*3.14锛岃繖灏辨槸鍦嗛敟搴曢潰鐨勫懆闀匡紝鎵浠ュ叾搴曢潰鍗婂緞锛2*3.14/2/3.14=1
绛旓細鎵囧舰鐨勫姬闀跨瓑浜庡渾閿ョ殑搴曢潰鍛ㄩ暱锛屼负 3*120*蟺/180=2蟺 锛屽渾閿ュ簳闈鍗婂緞涓 2蟺/(2蟺)=1 锛屽渾閿ョ殑琛ㄩ潰绉=1/2*2蟺*3+蟺*1^2=4蟺 锛岀敱浜庡渾閿ョ殑楂 h=鈭(3^2-1^2)=2鈭2 锛屾墍浠ュ渾閿ョ殑浣撶НV=Sh/3=2鈭2蟺/3 銆
绛旓細120搴=2蟺/3 杩欎釜鎵囧舰闈㈢Н鏄細1/2x2蟺/3x3²=蟺/3x9 =3蟺锛坈m²锛
绛旓細鎵囧舰鐨勯潰绉紳3²脳3.14脳120/360锛9.42骞虫柟鍘樼背 鎵囧舰鐨勫懆闀匡紳3脳2脳3.14脳120/360+3+3=12.28鍘樼背
