To complete Peter's thought...
mysql> set @x=743.7585697483, @y=743.5888244369;
mysql> create table f412178(
-> decx decimal(15,10), decy decimal(15,10),
-> dblx DOUBLE, dbly DOUBLE);
mysql> insert into f412178 values
-> (743.7585697483,743.5888244369, 743.7585697483,743.5888244369),
-> (@x,@y, @x,@y);
mysql> SELECT decx/decy, dblx/dbly FROM f412178;
+------------------+-----------------+
| decx/decy | dblx/dbly |
+------------------+-----------------+
| 1.00022827845958 | 1.0002282784596 |
| 1.00022827845958 | 1.0002282784596 |
+------------------+-----------------+
mysql> select decx, decy, ln(decx/decy),
-> dblx, dbly, ln(dblx/dbly)
-> from f412178;
+----------------+----------------+---------------------+----------------+----------------+---------------------+
| decx | decy | ln(decx/decy) | dblx | dbly | ln(dblx/dbly) |
+----------------+----------------+---------------------+----------------+----------------+---------------------+
| 743.7585697483 | 743.5888244369 | 0.00022825240801256 | 743.7585697483 | 743.5888244369 | 0.00022825240801278 |
| 743.7585697483 | 743.5888244369 | 0.00022825240801256 | 743.7585697483 | 743.5888244369 | 0.00022825240801278 |
+----------------+----------------+---------------------+----------------+----------------+---------------------+
Notice the slight difference between DECIMAL and DOUBLE.