dailysudoku.com

[reliantrobin]

I've filled in the easy numbers and have reached the point where I believe I have no option but to make a guess for my next move:

1--2---398
843-92---
---38-2--
---9--853
---------
538--69--
--1-79---
---52--67
-2------9

The tip is R4C1 = 2, but I believe R5C1 could equally well be 2. What am I missing?

[chobans]

Next logical step should be:

r4c5 can only be 1,4
r4c6 can only be 1,4,7
r6c5 can only be 1,4

Since r4c5 and r6c5 can only be two numbers, we can elminate these two numbers from the other cells in the square (r4c4 - r6c6). So that means r4c6 can only be a 7.

[reliantrobin]

Many thanks. Now I can sleep tonight.

[Guest]

R5C1 cannot be 2 as it would prevent a 2 being placed in the square:
Rs 456 Cs789. However you would have had to deduce that R5C4 is 8 and R6C4 is 2 before realising this.