Hình a
\(\Delta ABC\) có:
\(\widehat{A}+\widehat{B}+\widehat{C}=180^0\) (tổng ba góc trong \(\Delta ABC\))
\(70^0+x+38^0=180^0\)
\(\Rightarrow x=180^0-\left(70^0+38^0\right)\)
\(=72^0\)
Vậy ∠B = 72⁰
------------------------------
Hình b
\(\Delta DEF\) có:
\(\widehat{D}+\widehat{E}+\widehat{F}=180^0\) (tổng ba góc trong \(\Delta DEF\))
\(y+40^0+50^0=180^0\)
\(\Rightarrow y=180^0-\left(40^0+50^0\right)\)
\(=90^0\)
Vậy \(\widehat{D}=90^0\)
-------------------------------------
\(\Delta GHI\) có:
\(\widehat{G}+\widehat{H}+\widehat{I}=180^0\) (tổng ba góc trong \(\Delta GHI\))
\(z+41^0+35^0=180^0\)
\(\Rightarrow z=180^0-\left(41^0+35^0\right)\)
\(=104^0\)
Vậy \(\widehat{G}=104^0\)
