tìm số đo các góc cuả hình thang ABCD ( AB song song CD) biết: A+3B=210 độ; 3A=2C 13/08/2021 Bởi Savannah tìm số đo các góc cuả hình thang ABCD ( AB song song CD) biết: A+3B=210 độ; 3A=2C
Ta có: $\widehat{A}+\widehat{C}=180^o$ $↔ 3\widehat{A}+3\widehat{C}=540^o$ $↔ 2\widehat{C}+3\widehat{C}=540^o$ $↔ 5\widehat{C}=540^o$ $↔ \widehat{C}=108^o$ $→ \widehat{A}=180^o-\widehat{C}=72^o$ $\widehat{B}=(210^o-\widehat{A}):3=46^o$ $\widehat{D}=180^o-\widehat{B}=134^o$ Bình luận
Ta có:
$\widehat{A}+\widehat{C}=180^o$
$↔ 3\widehat{A}+3\widehat{C}=540^o$
$↔ 2\widehat{C}+3\widehat{C}=540^o$
$↔ 5\widehat{C}=540^o$
$↔ \widehat{C}=108^o$
$→ \widehat{A}=180^o-\widehat{C}=72^o$
$\widehat{B}=(210^o-\widehat{A}):3=46^o$
$\widehat{D}=180^o-\widehat{B}=134^o$