Geometry problem (27)


Problem
Calculate the value of angle x in the picture below.














Solution



Point E is the reflexion of B over line AC.
Draw the circle through points A,B and E.
LBEA = (180-40)/2=70
Point D positioned on the circle because LACD = (boogAE - 20)/2 = 60 {Thales rules}

x = 140/2 = 70

Note: arc lengths are written red.