Im sure this question has been asked and answered before, but I can find anything previous threads on it.

Does the dual casting perk work on master level spells?

With the dual casting perk if I cast Guardian Circle with the perk will it repel undead up to level 77? (35x2.2)
If dual casting doesnt work on master level spells would dual casting circle of protection raise the level cap of the spell?
Also how much does nercomage raise the level cap.

And one final question. Dual casting illusion spells, do you need all the perks (kindred mage+Aspect of terror) to hit the cap or can I just take one dual cast and still hit the enemy level cap (which I heard was about 50)

No it does not, as far as I can tell, as they all require both hands to cast anyway...

With Illusion spells you would need to have all the perks for the master levels to be effective unless the master level spells in Illusion actually ARE affected by the Dual Casting perk... Though I find that Illusion spells never seem to dual cast as they are supposed to anyway...

I can't guarantee that my information is correct though...