step 11
Prove
DB=AC
Applying Pythagorean theorem
Right triangle ADB
AB^2=AD^2+DB^2 ------> DB^2=AB^2-AD^2
Right triangle BCA
AB^2=BC^2+AC^2 -----> AC^2=AB^2-BC^2
Remember that
AD=BC
by substitution
AC=DB
step 12
triangle ADB is congruent to triangle BCA by SSS