a) Ta có:
\(\left\{{}\begin{matrix}m\perp AB\left(gt\right)\\n\perp AB\left(gt\right)\end{matrix}\right.\)
=> \(m\) // \(n\) (từ vuông góc đến song song).
b) Ta có: \(\widehat{ADC}+\widehat{mDC}=180^0\) (vì 2 góc kề bù).
=> \(110^0+\widehat{mDC}=180^0\)
=> \(\widehat{mDC}=180^0-110^0\)
=> \(\widehat{mDC}=70^0.\)
Vì \(m\) // \(n\left(cmt\right)\)
=> \(\widehat{mDC}=\widehat{C}\) (vì 2 góc đồng vị).
Mà \(\widehat{mDC}=70^0\left(cmt\right)\)
=> \(\widehat{C}=70^0.\)
Vậy \(\widehat{C}=70^0.\)
Chúc bạn học tốt!
Ta có :
\(\left\{{}\begin{matrix}m\perp AB\\n\perp AB\end{matrix}\right.\)
\(\Leftrightarrow m\backslash\backslash n\left(đpcm\right)\)
\(\Leftrightarrow\widehat{ADC}+\widehat{BCD}=90^0\) (hai góc trong cùng phía)
\(\Leftrightarrow\widehat{BCD}=180^0-110^0=70^0\)
Vậy..
câu a) vì sao m//n nhé
a)Ta có:
m⊥AB
n⊥AB
⇒m//n
b)Vì m//n
⇒ADC+DCB=1800
⇒1100+DCB=1800
⇒ DCB=1800-1100
⇒ DCB=700
Vậy góc C =700
