Question

in figure 4.43 ab is parallel to CD find the value of angle fce

Answer 1

as ab||cd then
<abf = < dfe = 80° ( corresponding angles )
But , <dfe + <efc = 180° ( linear pair )
80 + <efc = 180
<efc = 100°
then , in ∆ cef
< cef + < cfe < ecf = 180° ( angle sum property of triangles )
45 + 100 + < fce = 180
<fce = 180-145
< fce = 35°

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