View Full Version : Derivatives:miscellaneous application
akotoh
Aug 22, 2009, 04:06 PM
Please help me find the derivatives of the following:
1.) log(3/x)
2.) ln cot 1/2 x
Remenciements d'avance! :)
galactus
Aug 22, 2009, 05:03 PM
2.) ln cot 1/2 x
Chain rule. Derivative of inside times derivative of outside.
The derivative of ln(u)=1/u. Since u=cot(x/2), then we have \frac{1}{2}cot(\frac{x}{2})
Derivative of inside is the derivative of cot(\frac{x}{2})=\frac{-1}{2}csc^{2}(\frac{x}{2})
Multiply them and simplify:
\frac{1}{cot(\frac{x}{2})}\cdot \frac{-1}{2}csc^{2}(\frac{x}{2})
=\frac{-1}{2sin(\frac{x}{2})cos(\frac{x}{2})}
Remenciements d'avance! :)[/QUOTE]
radiation
Aug 24, 2009, 07:16 AM
Chain rule. Derivative of inside times derivative of outside.
The derivative of ln(u)=1/u. Since u=cot(x/2), then we have \frac{1}{2}cot(\frac{x}{2})
Derivative of inside is the derivative of cot(\frac{x}{2})=\frac{-1}{2}csc^{2}(\frac{x}{2})
Multiply them and simplify:
\frac{1}{cot(\frac{x}{2})}\cdot \frac{-1}{2}csc^{2}(\frac{x}{2})
=\frac{-1}{2sin(\frac{x}{2})cos(\frac{x}{2})}
Remenciements d'avance! :)[/QUOTE]
it can further be reduced to -1/sin(x) =-csc(x)
{2 sinAcosA = sin 2A}
Unknown008
Aug 24, 2009, 12:11 PM
Of course radiation. If further simplification was required, then that would be the OP's work. :)