Question 38In this diagram $\overline{AB}$ and $\overline{AC}$ are the equal sides of an isosceles triangle $ABC,$ in which is inscribed equilateral triangle $DEF.$ Designate angle $BFD$ by $a,$ angle $ADE$ by $b,$ and angle $FEC$ by $c.$ Then: $b=\dfrac{a+c}{2}$$b=\dfrac{a-c}{2}$$a=\dfrac{b-c}{2}$$a=\dfrac{b+c}{2}$none of these
