Question

F(x)=2secx+tanx 0 11 years ago

Answer 1

find the derivative?

Answer 2

set it =0

Answer 3

i know that... how do i find the derivatives.

Answer 4

eyust707 take the derivative for her :0)

Answer 5

okay

Answer 6

you find the derivative of each term seprate

Answer 7

lets look at the first term

Answer 8

secx=secxtanx and tanx=secx^2. but what do you do with the 2 in front of the secx

Answer 9

the two is a constant is just hangs out in front

Answer 10

yup

Answer 11

so, when finding derivatives it just stays? so the answer for the derivative would be 2secxtanx + secx^2?

Answer 12

yep

Answer 13

you don't have to use the product rule or whatever?

Answer 14

product rule is when you there are two variable in the same term

Answer 15

and 2 isn't a variable? ha. alright. got it.

Answer 16

like tanxsecx would need product rule

tanx+secx would not

Answer 17

yeah i know. but the 2 is being multiplied...

Answer 18

yea but the 2 is not a variable.. its a number

Answer 19

but the derivative of a number is 0. that's what messes me up

Answer 20

ahhh i see i see

Answer 21

so it just hangs out there then. well that's dumb. ha

Answer 22

yeah just like the derivative of 5*x^2

Answer 23

is 10x

Answer 24

oh got it. nice example.

Answer 25

the five stays bring the two down you get 2*5x

Answer 26

yep!

Answer 27

so when you are finding the critical points...

Answer 28

yes..

Answer 29

you set it equal to zero... so it would be 0=2secxtanx+secx^2. bring the secx out?

Answer 30

secx(2tanx+secx)?

Answer 31

yea its been a little wile since i did that but your math is def correct

Answer 32

good job brie

Answer 33

I just don't get it. then you would have to set the inside of the parenthesis to zero... and i don't know how to do that.

Answer 34

because they are two different trig terms.

Answer 35

2tanx+secx=0

Answer 36

yeah. and then what

Answer 37

well lets see not 100 percent sure but..

Answer 38

2tanx=-secx

Answer 39

tanx=sinx/cosx and secx = 1/cosx

Answer 40

brilliant! alright. thank you

Answer 41

wait wait wait. still don't get it.

Answer 42

2sinx/cosx+1/cosx=2sinx/cosx

Answer 43

its been hella days since i did these alvin you got these down?

Answer 44

eliminate one of the trig functions and leave x on one side i think

Answer 45

yeah... ha. but which one can be eliminated?

Answer 46

sinx+1/cosx

Answer 47

2tanx+cosx=1

Answer 48

2tanx=1-cosx

Answer 49

i thought it equaled 0?

Answer 50

i think theres a rule for 1-cosx??

Answer 51

hehe i messed up

Answer 52

2tanx+secx=0

Answer 53

thought you took the derivative before?

Answer 54

that is what we ended up with

Answer 55

now we are trying to find the critical points.

Answer 56

for the derivative we ended up with secx(2tanx+secx)=0

Answer 57

lets start from where we were

2tanx=-secx

2tanx= -1/cosx

2tanxcosx= -1

tanxcosx=-1/2

sinxcosx/cosx=-1/2

Answer 58

brilliant!

Answer 59

sooo...

Answer 60

so sinx=-1/2 and that's at 7pii/6

Answer 61

and 11pii/6

Answer 62

for the secx=0

Answer 63

1/cosx=0?

Answer 64

that DNE

Answer 65

why?

Answer 66

1 over what number gives you zero?

Answer 67

because 1 doesn't equal 0 when you multiply both sides by cosx?

Answer 68

is there any number you can put in?

Answer 69

right.. got it. thank you.

Answer 70

well infinity would work... butt cosx is never greater than 1

Answer 71

kk i got a midterm in the mornin i gots to study for but if you got skype shoot me a message on there and id be glad to help. my name is exactly the same on there

Answer 72

wait... did we mess up

Answer 73

lol maybe

Answer 74

ohh nvm haha. thank gosh

Answer 75

thanks for all the help.

Answer 76

welcome =)