f(x) := x.cos(x) - sin(x) . Plotting local max-min-points ?

[lvl107]

Hello Everyone.

f(x) := x.cos(x) - sin(x) . Plotting local max-min-points ?

Thanks in advance.
Regards.

[lvl107]

And : x.cos(x) - sin(x) solve, x ==> 10 solutions.

Regards.

[Werner_E · Accepted solution]

You expect different answers than here

https://community.ptc.com/t5/PTC-Mathcad/x-cos-x-sin-x-0-solve-x/m-p/578062/highlight/true#M183000 

ore here

https://community.ptc.com/t5/PTC-Mathcad/Plotting-local-max-min-points/m-p/578354/highlight/true#M183021

?

Put your math together! You have to find the zeros of the first derivative. Either symbolically or numerically. You have all the tools necessary at hand!

Simply exclude those where the second derivative is zero, too. To be mathematically more precise you should exclude those where the first derivative with non-zero value is of an odd degree.