Đáp án:$S_{DNKM}=100\sqrt{3}$
Giải thích các bước giải:
Ta có:
$S_{DNKM}=S_{KDM}+S_{KDN}$
$\to S_{DNKM}=\dfrac{DM}{DE}\cdot S_{KDE}+\dfrac{DN}{DF}\cdot S_{KDF}$
$\to S_{DNKM}=\dfrac{DM}{DE}\cdot \dfrac12S_{DEF}+\dfrac{DN}{DF}\cdot\dfrac12 S_{DEF}$
$\to S_{DNKM}=\dfrac12S_{DEF}(\dfrac{DM}{DE}+\dfrac{DN}{DF})$
$\to S_{DNKM}=\dfrac12S_{DEF}(\dfrac{FH}{FE}+\dfrac{EH}{EF})$ vì $HM//DF, NH//DE$
$\to S_{DNKM}=\dfrac12S_{DEF}\cdot \dfrac{FH+EH}{EF}$
$\to S_{DNKM}=\dfrac12S_{DEF}\cdot \dfrac{EF}{EF}$
$\to S_{DNKM}=\dfrac12S_{DEF}\cdot 1$
$\to S_{DNKM}=\dfrac12S_{DEF}$
$\to S_{DNKM}=100\sqrt{3}$