For each of the differential equations in question, find a particular solution satisfying the given condition:
dy/dx = y tan x; y = 1 when x = 0
Separating variables,
Integrating both sides,
⇒ log y = -log (cos x) + log c
Or,
⇒ log y = log (sec x) + log c
⇒ log y = log c (sec x)
⇒ y = c (sec x) -i)
Now we are given that y = 1 when x = 0
⇒ 1 = c (sec 0)
⇒ 1 = c × 1
⇒ c = 1
Putting the value of c in i)
⇒ y = sec x