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