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Hallo nuages

A longer explanation (ravel was quicker):

The 6 in col9 forces row6 to have its 6 in box4.

Thus there won't be a 6 in the rest of box4.
This includes r5c2, leaving it with only {5,9} ...

Hallo LT

Check out how row3 and box8 affect col6.

Same hint, different approach:
check out the Code.

To those who found it without profiling, how did it emerge?
For me, being a few days behind, this topic title was a spoiler.
So it didn't emerge.

Sarah,
Seeing what can be in r2c3 and r5c3 isn't conclusive here.
The argument goes in two steps:
- see what can't go in certain cells
- what can't go there must be accomodated in the other cells.
...

so I ignored the triplet 469 - that lead to the 35
I was going to remark that it is not necessary to recognise the triplet, but you have now demonstrated that yourself.

On the other hand this was a p ...

Hallo Sarah

You already have a 4 in column 2.

You can get more control over the layout
by putting your grid numbers between 'code' tags.
You type in something like

[code]grid_numbers ...

Hallo Huh

The conventional explanation is that the two empty cells at the bottom of col3 can both take only the values 2 or 7, i.e. their candidate lists are {2,7}. Thus between them they must cont ...

When you evaluate the possible values of r4c7 and r4c8 you get {8,9} for both of them.

[It seemed quite a coincidence to me, but maybe it isn't;
All the constraints except the 3 arise from row4 and ...

Hallo daykart

I would never see the quad either,
but maybe you would have a better chance at seeing the (complementary) pair instead?

This is particularly meaningful for cell r6c7 i.e. that r6c7 c ...

with minimal resources
Minimal boredom in my case.
I time out after getting nowhere for 15' or so.

Hallo Alan

F) This is the point at which one needs to consider the
transition to Candidate Profiles -
.
.
.

The grid at this stage has
67- --- -89
938 762 --1
--1 98- 7-6

1-- --- 9--
8-3 ...

Hallo igolf4birdies

May I suggest (my favorite constellation) a [url=http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=248]Glassman pan whose lid would be at r3b1?

We don't know what is in ...

Hallo akif

One way forward is to see that r7c4 and r7c6 between them contain 3 and 8 and nothing else, i.e. {3,8}.
Although we don't know exactly where this 3 is, it affects what can be a 3 in box9, ...

I'm not quite sure what you mean by citing a "pan" here.Follow my link above (and read your comments).

The triplet r4c7..9 is shared by row4 and box6, so
the rest of the row (the handle) has the sa ...

Hallo David

I sailed through this one on the day and wondered why it wasn't classed as medium.
But it certainly didn't seem medium when I looked at it again today in the context of this thread.
Thi ...

See also the discussion [url=http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=337]here.

I reserve erasure for correcting (immediately recognised) mistakes.

Hallo Brenda

Looking at col5, there are 3s scattered to the left and right of it, each doing its own bit of exclusion. In fact they exclude 3 from every free cell in col5 except the hint's row1 cell ...

I understand the bit about the pair of (2,5)s in column 5, box 8
Ok, that was the first intermediate step.
Its result is (partially) used later on when talking about r7c5.

but am completely in the d ...

If you want that to be your next cell, you need the following preparation:

The values 2 and 5 in col4 and col6 force col5 to have these values in box 8, i.e. r7..8c5 are a {2,5} pair.

The 7s in row ...

Have a look hidden is to some extent an artefact of working with full candidate lists: such pairs are buried under the mass of candidates.
They can often be discovered as a plain pair after going a di ...