求各种形状的周长和面积急···········································································································
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求各种形状的周长和面积急···········································································································
求各种形状的周长和面积
急···············································································································································································································································································
求各种形状的周长和面积急···········································································································
圆：面积=πr^2
周长=2πr
椭圆周长公式：L=2πb+4(a-b)
椭圆面积公式：S=πab
长方形的周长=（长+宽）×2
正方形的周长=边长×4
长方形的面积=长×宽
正方形的面积=边长×边长
三角形的面积 周长：三条边相加
已知三角形底a,高h,则S＝ah/2
已知三角形三边a,b,c,半周长p,则S＝ √[p(p - a)(p - b)(p - c)] （海伦公式）（p=(a+b+c)/2）
和：（a+b+c)*(a+b-c)*1/4
已知三角形两边a,b,这两边夹角C,则S＝absinC/2
设三角形三边分别为a、b、c,内切圆半径为r
则三角形面积=(a+b+c)r/2
设三角形三边分别为a、b、c,外接圆半径为r
则三角形面积=abc/4r
已知三角形三边a、b、c,则S＝ √{1/4[c^2a^2-((c^2+a^2-b^2)/2)^2]} (“三斜求积” 南宋秦九韶）
| a b 1 |
S△=1/2 * | c d 1 |
| e f 1 |
【| a b 1 |
| c d 1 | 为三阶行列式,此三角形ABC在平面直角坐标系内A(a,b),B(c,d),C(e,f),这里ABC
| e f 1 |
秦九韶三角形中线面积公式:
S=√[(Ma+Mb+Mc)*(Mb+Mc-Ma)*(Mc+Ma-Mb)*(Ma+Mb-Mc)]/3
其中Ma,Mb,Mc为三角形的中线长.
平行四边形的面积=底×高 周长 ：（a+b）*2
梯形的面积=（上底+下底）×高÷2 周长：四条边相加
圆的周长=圆周率×直径=
圆周率×半径×2
圆的面积=圆周率×半径×半径
长方体的表面积=
（长×宽+长×高＋宽×高）×2
正方体的表面积=棱长×棱长×6
圆柱的侧面积=底面圆的周长×高
圆柱的表面积=上下底面面积+侧面积
长方形：周长：（a+b）×2 面积：a×b
正方形：周长：4×a 面积：a²
三角形:周长：三条边相加 面积：底×高÷2
梯形：周长：四条边相加 面积：（上底+下底）×高÷2
圆形：周长：直径×圆周率 面积：半径²×圆周率
长方形周长2（a+b）面积ab正方形周长4a面积a^2 三角形面积ah/2周长a+b+c 梯形面积（a+b）h/2