Differentiate each of the following functions from the first principal :
log cos x
We have to find the derivative of log cosx with the first principle method, so,
f(x) = log cos x
by using the first principle formula, we get,
f ‘(x) =
f ‘(x) =
f ‘(x) =
f ‘(x) =
[Adding and subtracting 1]
f ‘(x) =
[Rationalising]
f ‘(x) =
[By using limx→0 = 1]
f ‘(x) =
[cosC – cosD = –2 sin sin]
f ‘(x) = [By using limx→0 = 1]
f ‘(x) =
f ‘(x) = – tan x