how to differentiate ln(cos x) w.r.t x by first principles
Asked by
| 24th Mar, 2008,
03:03: PM
Expert Answer:
F(x)=Log cosx
F(x+h)=log cos(x+h)
dy/dx =lim(h0) F(x+h)-F(x) / h
=lim(h0)Log cos(x+h) -logcosx /h
=lim(h0)Log cos(x+h)/cosx /h
=lim(h0)log(1+ cos(x+h)/cosx -1) /h
=lim(h0)log(1+cos(x+h)-cosx /cosx) /h
using C and D formula of trigo ...and lim (h0) log(1 + x) /x =1)
we get d/dx= -tanx
Answered by
| 2nd Apr, 2008,
05:11: PM
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