Hello,
\(\widehat{ABD}=\frac{180-40}{2}\)=70 (sum of angles of a triangle=180°)
\(\widehat{ABE}=180-70=110\) supplementary angles
\(\widehat{ABE}=\widehat{DCF}\) translation BC
\(\widehat{BCF}=110-40=70\) image of the angle DAB by the axis symmetry DB
\(\widehat{BCF}=\widehat{BEF}\) opposed angles of a parallelogram
are supplementary.
\(\widehat{BEF}=\widehat{HEG}\) opposed angles by the vertex
\(\widehat{HEG}=\widehat{IHE}=70\) alterne-interne angles (sorry for the words English is difficult for me)
