# How to obtain POS from the Karnaugh map?

I know there is a way of getting both without having to draw two maps, which is to draw the minterms on the map and then the Maxterms and organize them in groups just like the minterms.

My question is, what to do next? I've read in a book that the way to do it is to write the maxterms as minterms, like you would for a SOP, and then take the complement. In my professor's solutions there's an exercise he solved by writing the minterms direct as maxterms (ie: cd' = (c+d')). I'm confused. Here's his solution:

I could just ask him but I don't want to be that person and I've already pointed out a mistake in another solution, so... He also wrote "POS" above the one for the SOP and SOP above this one so I am a bit confused.

• "don't want to be that person" - If the professor has made mistakes before, you should take the opportunity to point it out again - not for brownie points, but because others will most likely benefit from it. There might be someone with your exact question not learning because of a mistake on the professors side - you might be "that person" but at least you are not objectively in the wrong. Jan 4, 2020 at 21:21
• @QuickishFM So am I correct and my professor did make a mistake? Jan 4, 2020 at 21:23
• That solution in the second image is a product of sums - if he's called it SOP, then yes, he's made a mistake here. I would not only ask for clarification on his naming of SOP for a supposed POS but also about how he did the solution there. cd' is NOT (c+d') - unless you are using DeMorgan's theorem, in which case it should be (c'+d)' Jan 4, 2020 at 21:25
• Have you tried this video? youtube.com/watch?v=xZOQRR_SYHs It seems to be good in explaining how to convert an SOP to POS using DeMorgans theorem. If you know DeMorgan's theorem then this video should be very straightforward Jan 4, 2020 at 21:29
• ... doing this stuff in the spotlight under the scrutiny of a bunch of people who expect infallibility is a tall order. As long as you are respectful and apply an appropriate tone, your classmates and the professor will surely appreciate an engaged audience. Jan 4, 2020 at 23:12