So where did the H point come from?
When point P approaches point C, the abscissa of point E is infinite, so ME is almost parallel to CB. At this time, point h almost coincides with point C.
At this time, just calculate the degree of H rotation. H rotation and ∠EMC complementary angle. Just ask ∠EMC.
When point P coincides with the origin, it is found that ∠EMC is equal to 135. You should know everything after that.