13 Find a particular solution of the differential equation 
cot
dy
y
x
dx +
 = 4x cosec x
(x ≠ 0), given that y = 0 when 
2
x
=π 14 Find a particular solution of the differential equation (x + 1) dy
dx  = 2 e–y – 1,  given
that y = 0 when x = 0