Question 79
Let $\Gamma$ be a half circle with diameter $AB$. Let $C$ be the point on the diameter, and let $D$ and $E$ be the points on the half circle so that $E$ lies between $B$ and $D$. It turns out that $\angle ACD = \angle ECB$. Let $F$ be the point of intersection of the lines tangent to $\Gamma$ at the points $D$ and $E$. Show that $\angle EFD = \angle ACD + \angle ECB$.