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OpenStudy (eyust707):
find the derivative?
OpenStudy (anonymous):
set it =0
OpenStudy (anonymous):
i know that... how do i find the derivatives.
OpenStudy (anonymous):
eyust707 take the derivative for her :0)
OpenStudy (eyust707):
okay
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OpenStudy (eyust707):
you find the derivative of each term seprate
OpenStudy (eyust707):
lets look at the first term
OpenStudy (anonymous):
secx=secxtanx and tanx=secx^2. but what do you do with the 2 in front of the secx
OpenStudy (eyust707):
the two is a constant is just hangs out in front
OpenStudy (anonymous):
yup
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OpenStudy (anonymous):
so, when finding derivatives it just stays? so the answer for the derivative would be 2secxtanx + secx^2?
OpenStudy (eyust707):
yep
OpenStudy (anonymous):
you don't have to use the product rule or whatever?
OpenStudy (eyust707):
product rule is when you there are two variable in the same term
OpenStudy (anonymous):
and 2 isn't a variable? ha. alright. got it.
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OpenStudy (eyust707):
like tanxsecx would need product rule
tanx+secx would not
OpenStudy (anonymous):
yeah i know. but the 2 is being multiplied...
OpenStudy (eyust707):
yea but the 2 is not a variable.. its a number
OpenStudy (anonymous):
but the derivative of a number is 0. that's what messes me up
OpenStudy (eyust707):
ahhh i see i see
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OpenStudy (anonymous):
so it just hangs out there then. well that's dumb. ha
OpenStudy (eyust707):
yeah just like the derivative of 5*x^2
OpenStudy (anonymous):
is 10x
OpenStudy (anonymous):
oh got it. nice example.
OpenStudy (eyust707):
the five stays bring the two down you get 2*5x
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OpenStudy (eyust707):
yep!
OpenStudy (anonymous):
so when you are finding the critical points...
OpenStudy (eyust707):
yes..
OpenStudy (anonymous):
you set it equal to zero... so it would be 0=2secxtanx+secx^2. bring the secx out?
OpenStudy (anonymous):
secx(2tanx+secx)?
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OpenStudy (eyust707):
yea its been a little wile since i did that but your math is def correct
OpenStudy (anonymous):
good job brie
OpenStudy (anonymous):
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.
OpenStudy (anonymous):
because they are two different trig terms.
OpenStudy (eyust707):
2tanx+secx=0
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OpenStudy (anonymous):
yeah. and then what
OpenStudy (eyust707):
well lets see not 100 percent sure but..
OpenStudy (eyust707):
2tanx=-secx
OpenStudy (eyust707):
tanx=sinx/cosx and secx = 1/cosx
OpenStudy (anonymous):
brilliant! alright. thank you
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OpenStudy (anonymous):
wait wait wait. still don't get it.
OpenStudy (anonymous):
2sinx/cosx+1/cosx=2sinx/cosx
OpenStudy (eyust707):
its been hella days since i did these alvin you got these down?
OpenStudy (anonymous):
eliminate one of the trig functions and leave x on one side i think
OpenStudy (anonymous):
yeah... ha. but which one can be eliminated?
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OpenStudy (anonymous):
sinx+1/cosx
OpenStudy (eyust707):
2tanx+cosx=1
OpenStudy (eyust707):
2tanx=1-cosx
OpenStudy (anonymous):
i thought it equaled 0?
OpenStudy (eyust707):
i think theres a rule for 1-cosx??
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OpenStudy (eyust707):
hehe i messed up
OpenStudy (anonymous):
2tanx+secx=0
OpenStudy (anonymous):
thought you took the derivative before?
OpenStudy (anonymous):
that is what we ended up with
OpenStudy (anonymous):
now we are trying to find the critical points.
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OpenStudy (anonymous):
for the derivative we ended up with secx(2tanx+secx)=0
OpenStudy (eyust707):
lets start from where we were
2tanx=-secx
2tanx= -1/cosx
2tanxcosx= -1
tanxcosx=-1/2
sinxcosx/cosx=-1/2
OpenStudy (anonymous):
brilliant!
OpenStudy (eyust707):
sooo...
OpenStudy (anonymous):
so sinx=-1/2 and that's at 7pii/6
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OpenStudy (anonymous):
and 11pii/6
OpenStudy (anonymous):
for the secx=0
OpenStudy (anonymous):
1/cosx=0?
OpenStudy (eyust707):
that DNE
OpenStudy (anonymous):
why?
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OpenStudy (eyust707):
1 over what number gives you zero?
OpenStudy (anonymous):
because 1 doesn't equal 0 when you multiply both sides by cosx?
OpenStudy (eyust707):
is there any number you can put in?
OpenStudy (anonymous):
right.. got it. thank you.
OpenStudy (eyust707):
well infinity would work... butt cosx is never greater than 1
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OpenStudy (eyust707):
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
OpenStudy (anonymous):
wait... did we mess up
OpenStudy (eyust707):
lol maybe
OpenStudy (anonymous):
ohh nvm haha. thank gosh
OpenStudy (anonymous):
thanks for all the help.
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