`sec^(2)xtan y dx+sec^(2)ytan xdy=0`

Explanation

`sec^(2)xtan y dx+sec^(2)ytan xdy=0`
`implies (sec^(2)x)/(tan x)dx+(sec^(2)y)/(tany)dy=0`
`implies int (sec^(2)x)/(tanx)dx+int(sec^(2)y)/(tan y)dy=c_(1)`
`implies int(1)/(t)dt+int(1)/(z)dz=c_(1)`
implies log t + log z = log c
implies t.z = c
implies tan x. tan y = c
माना tan x = t `implies sec^(2)x dx = dt` और tan y = z `implies sec^(2)y dy = dz` (जहाँ `c_(1)=logc`)