Examples
Ex 1:
y = cos x . cos 2x . cos 3x . . . . . . .cos nx, then y ' is
Sol:
Given that y = cos x . cos 2x . cos 3x. . . . . . . cos nx
⇒ log y = log (cos x) + log (cos 2x ) + log (cos 3x) + . . . . + log (cos nx)
⇒ y ' = – y (tan x + 2 tan 2x + 3 tan 3x + . . . . n tan nx)
Ex 2:
y = xx
Sol:
| log y | = | log xx |
| log y | = | x . log x |
 . |
= | x .  + log x |
|
= | y (1 + log x) |
| ∴ y ' | = | xx(1 + log x) |
Ex 3:
y = 
Sol:
Ex 4:
y = 
, then y' is
Sol:
Ex 5:
Sol:
