Multiple hellos. It is 30 degrees.
Solution: (All angular measurements in degrees)
is an altitude and is a median and is on the line
If is an altitude, then and are .
Filling in relevant angles angles: ,
A median splits a triangle into two triangles equal in area.
Construct altitude . (dotted line in diagram, forgot to label O)
Two similar triangles are discovered, and (as and are parallel)
Calculate area of
(Because a median splits a triangle into two triangles equal in area.)
Which means that and
Hence and are identical