平行四邊形面積公式的推導過程?四邊形兩條邊分别是a,b夾角αS=(1/2absinα)*2=absinα，下面我們就來聊聊關于平行四邊形面積公式的推導過程?接下來我們就一起去了解一下吧!
四邊形兩條邊分别是a,b夾角α
S=(1/2absinα)*2=absinα
對角線c1,c2
a^2+b^2-2abcosα=c1^2
a^2+b^2-2abcos(180-α)=c2^2
a^2+b^2+2abcosα=c2^2
c2^2-c1^2=4abcosα
(c2^2-c1^2)/4=abcosα
(abcosα)^2+(absinα)^2=(ab)^2
((c2^2-c1^2)/4)^2+s^2=(ab)^2
s^2=(ab)^2-((c2^2-c1^2)/4)^2
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