求英语语法问题:to which

Question

In more mathematical or scientific terms, it is a measure of the extent to which input is well used for an intended task or function (output).
这里的to which是什么情况？

Answer 1

to which在这里是定语从句修饰the extent
定语从句的其中一类表达方式：先行词+介词+关系代词(这里介词用什么取决于先行词)
to some extent：在某种程度上

Answer 2

the extent to wihch, 整体记住吧！在牛津英文词典上：the degree to which something happens or is likely to happen
e.g. She had not realized the extent to which the children had been affected.

Answer 3

这句话可以这么拆开为两句 It is a measure of the extent.
Input is well used for an intend task or function to the extent.
which在此引导定语从句，两句话合并成一句时要用倒装，也就是the extend to，并没有to which这种用法。