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Mathematics 22 Online
OpenStudy (anonymous):

need help on the attachment

OpenStudy (anonymous):

OpenStudy (anonymous):

are you looking for the derivative of \[\tan(x)(2+\csc(x))\]?

OpenStudy (anonymous):

hard to read, but if so forget the product rule and multiply out. you get \[2\tan(x)+\sec(x)\] and then take the derivative term by term

OpenStudy (anonymous):

what is this?

OpenStudy (anonymous):

derivative of Tan x(2+csc x)

OpenStudy (anonymous):

got it

OpenStudy (anonymous):

turn it in to \[2\tan(x)+\sec(x)\] first

OpenStudy (anonymous):

then the derivative of tangent is secant squared, and the derivative of secant is secant tangent

OpenStudy (anonymous):

so right away you get \[2\sec^2(x)+\sec(x)\tan(x)\]

OpenStudy (anonymous):

ok

OpenStudy (anonymous):

but its doesn't match one of the answer choices

OpenStudy (anonymous):

ok i see that so it is trig identity time. the calc is over

OpenStudy (anonymous):

ok, lol

OpenStudy (anonymous):

factor out a \[\sec^2(x)\]

OpenStudy (anonymous):

how can you factor out sec^2(x) when the second term has only one sec (x) with tanx

OpenStudy (anonymous):

you get \[\sec^2(x)(2+\frac{1}{\sec(x)}\tan(x))\] \[\sec^2(x)(2+\cos(x)\tan(x))\] \[\sec^2(x)(2+\sin(x))\]

OpenStudy (anonymous):

good question i thought you might ask it

OpenStudy (anonymous):

great response, lol

OpenStudy (anonymous):

you factor it out by taking the reciprocal of secant, which is cosine

OpenStudy (anonymous):

oh, ok so its all about manipulation till this point

OpenStudy (anonymous):

all these things that are not sine and cosine are just combinations of them. so it is confusing, but they have no life of there own

OpenStudy (anonymous):

i mean you don't even have secant on your calculator right?

OpenStudy (anonymous):

no, but I do have cosine which you can just 1/cosx=secant

OpenStudy (anonymous):

exactly my point. you can dispense with it entirely. it is just something made up to confuse you

OpenStudy (anonymous):

and your next good question might be "how did you know to do that?"to which i would answer "well i saw the answers had a sec^2(x) factored out, so i factored it out"

OpenStudy (anonymous):

oh, ok so really the we just simplify the function because we already took the derivative in the first part

OpenStudy (anonymous):

right all the steps except the "take the derivative" step (only one step) was manipulating trig identities via algebra

OpenStudy (anonymous):

well thanks so much satellite!

OpenStudy (anonymous):

yw

OpenStudy (anonymous):

forgot to ask where did the cosine go at the end when it was pair with tangent

OpenStudy (anonymous):

????

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