Easier way to find trig stat points? (1 Viewer)

[enigma_1]

Eg for y=(e^-x)(cosx)

After finding the first derivative, how do you easily determine whether the point is maximum or minimum? It's tedious subbing in those values. Please help

 

[rumbleroar]

Find the second derivative and sub the x coordinate of the stat point in. If y" < 0, it is a maximum. If is > 0 it is a minimum.

 

[enigma_1]

Thanks mate!!

 

[enigma_1]

Can someone tell me what is the nature of the inflexion point at x=pi ?

Like how do you know what way it turns? because I'm getting something like u.n when I sub it into 2nd derivative

 

[youngsky]

Can someone tell me what is the nature of the inflexion point at x=pi ?

Like how do you know what way it turns? because I'm getting something like u.n when I sub it into 2nd derivative

If "u.n" is what you're getting, then it simply means "about the inflexion point, the concavity changes from concave up to concave down."