Question

Can someone please help me, i just need this question to earn an 100 in my homework:( i don't get it at all

Answer 1

calculate where 2nd deriv is equal to 0

Answer 2

i did !!!

Answer 3

wait no i didn't i don't get how with trigonometry involved

Answer 4

i know how to deriv but not these kind

Answer 5

derivative of sin is cos
derivative of cos is -sin

Answer 6

so f'(x) = 5cos(x) -5sin(x)
f"(x) = -5sin(x) - 5cos(x)

Answer 7

so then, where, from 0 to 2pi, does f"(x) = -5sin(x) - 5cos(x) = 0?

Answer 8

if x<0 or x>2pi, it doens't count

Answer 9

yea i knew that, but how do i put it in terms of webassign?

Answer 10

what values did you get for x?

Answer 11

yea, we exclude that part!! okay:)

Answer 12

no i meant i knew that sin derived is cos

Answer 13

so, what value of x satisfies:
-5sin(x) - 5cos(x) = 0

Answer 14

none, like with my other problems i would just factor after getting the 2nd derivative and then get the values from there

Answer 15

do u get what im saying?

Answer 16

thats how i did all my other examples

Answer 17

trigonomic functions are a bit different from polynomials like x^2-4=0

Answer 18

these values from 0, 2pie

Answer 19

yea, no wonder i can't do it and keep getting it wronG:/

Answer 20

well, we do some more algebra so we get sin(x)/cos(x) = 0

Answer 21

sin(x)/cos(x) is tan(x)

Answer 22

yes, identities are being used right?

Answer 23

so find when tan(x) = 0 between 0 and 2pi

Answer 24

er tan(x) =1

Answer 25

not tan(x) = 0

Answer 26

tan is simply sin over cosine so i just look for those values? im sorry im really bad at trig

Answer 27

actually tan(x) = -1

Answer 28

can u explain why please?

Answer 29

you can undo the tan function with the arctan aka\[\tan^{-1} \]function

Answer 30

so \[\tan^{-1}( \tan (x)) = \tan^{-1} (-1)\]which becomes\[x = \tan^{-1} (-1)\]

Answer 31

you can look up values on a trig table

Answer 32

okay yea i see!!! thank you for going through steps with me

Answer 33

so then after that?

Answer 34

plug the values you got back into the f(x), the original equation

Answer 35

the -1?

Answer 36

i dont get the steps at all im sorry i dont get this problem at all, i mean after you do it it makes sense but that all