In both triangles MAH and TAH,
MH = TH (Equally bisected by AH)
Angle MHA = Angle THA (Perpendicularly 90°)
AH = AH (Common)
By SAS rule,
Both triangles are congruent.
And by cpct (Conference part of Congruent triangles) AM will equal to AT.
!! Hope It Helps !!