In the diagram GI is a tangent to the circle at... - WAEC Mathematics 2010 Question

F = 54^o (Alternate triangle angles)

< GHE = F = 54^o(Angle between a chord and a tangent = angles in the alternate segment)

Now, < GHE + < EHF + < IHF = 180^o(Angles on a straight line)

54^o + < EHF + 54^o = 180^o

< EHF = 180^o - 108^o

= 72^o