AE = AC = 4
m<CAB = 60 (equilateral triangle)
m<CAE = 90 (square)
m<BAE = 150 (= 60 + 90)
Triangle BAE is isosceles since AB = AE;
therefore, m<AEB = m<ABE.
m<AEB + m<ABE + m<BAE = 180
m<AEB + m< ABE + 150 = 180
m<AEB + m<AEB = 30
m<AEB = 15
In triangle ABE, we know AE = AB = 4;
we also know m<BAE = 150, and m<AEB = 15.
We can use the law of sines to find BE.
BE/(sin 150) = 4/(sin 15)
BE = (4 sin 150)/(sin 15)
BE = 7.727
