Digital Teaching Aid (DED Philippinen, 86 p.) 
Introduction Boolean Algebra  Lesson 2 
Lesson Plan 

Augustus De Morgan was the first who found the link between logic and mathematics.
Fig. 28: Logic circuits with the
same output
Although the circuits are different but the output, as we can see in the truth table, is equal. Therefore we can write:
_{}De Morgan's First Theorem
Also if we compare the two circuits on the next page we can easily see that the output is the same, although the circuits are different.
(see Fig. 29)
Fig. 29: Logic circuits with the
same output
So we can write:
_{}De Morgan's Second Theorem
HO: How can you connect a NAND gate to get an inverter
Solution:
Figure
HO: How can you connect NAND gates to get an OR gate?
Solution:
Figure