Historical Note
One of the principal languages of Science is that of differential equations Interestingly, the date of birth of differential equations is taken to be November,
11,1675, when Gottfried Wilthelm Freiherr Leibnitz (1646 - 1716) first put in black
and white the identity 
212
y dy
y
=
∫
, thereby introducing both the symbols ∫ and dy © NCERT
not to be republished
DIFFERENTIAL EQUATIONS
423
Leibnitz was actually interested in the problem of finding a curve whose tangents
were prescribed This led him to discover the ‘method of separation of variables’
1691