AC=2*AD=2h,
DC=6
AB=10
h²=(4h^2-6^2)
3h²=36
h²=12
h=2√3=AD
CB=√(h²+(AB-DC)²)
CB=√(12+16)
CB=2√7
sin(XBC)=h/(CB)
sin(XBC)=2√3/2√7
sin(XBC)=√(3/7)
XBC≈41°
