Since you have a median that goes from the vertex to the midpoint of line a, which forms to right angles you can use SAS since line a and b are part of both triangles. That is if I understand how your triangle is set up.

I picture a big triangle cda with angle a at the vertex of cd, the median going to the midpoint of a, which then means they share side a also and you have two triangles acb and adb. If this is correct then you can use SAS if not, them try to provide a sketch of your triangle. Hope this helps.