Mathematics
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OpenStudy (anonymous):
Given: f'(x)=cscx(cotx-sin2x) what is f(x)?
note: sin2x=2sinxcosx
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OpenStudy (anonymous):
need a step by step explanation
OpenStudy (anonymous):
well this question is about integration
OpenStudy (anonymous):
sure will do
OpenStudy (anonymous):
yes
OpenStudy (anonymous):
im not sure what to do tho lol
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OpenStudy (anonymous):
not to worry follow my steps you'll get to know
OpenStudy (anonymous):
ok
OpenStudy (anonymous):
please confirm if i copied your question correctly: \[f'(x) = \csc(x)(\cot(x)-\sin(2x))\]
OpenStudy (anonymous):
yup
OpenStudy (anonymous):
ok good
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OpenStudy (anonymous):
ok
OpenStudy (anonymous):
my net is a bit slow today i need to format my computer but i sill show you all the steps ok
OpenStudy (jamesj):
*bookmark. I am curious to see if mathsmind ever gets to the end of an explaination in a finite amount of time
OpenStudy (anonymous):
lol ok
OpenStudy (anonymous):
you have been chasing me all day long mr james bond
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OpenStudy (anonymous):
ok the first step: is simplification
OpenStudy (anonymous):
ok.
OpenStudy (anonymous):
now you should know by definition what cscx =?
OpenStudy (anonymous):
ok recall
OpenStudy (anonymous):
\[\csc(x) = \frac{ 1 }{ \sin(x) }\]
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OpenStudy (anonymous):
1/sin
OpenStudy (anonymous):
good .. good
OpenStudy (anonymous):
ok so now do i integrate my new equation\'?
OpenStudy (jamesj):
Let's push this along a little, shall we?
\[ f'(x) = \csc(x)(\cot(x)−\sin(2x)) = \frac{\cos x}{\sin^2 x} - 2\cos x \]
yes?
OpenStudy (anonymous):
\[\int\limits \csc(x)(\cot(x)-\sin(2x))dx\]
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OpenStudy (anonymous):
no i will make it simpler
OpenStudy (anonymous):
\[\int\limits\limits\limits (\csc(x)\cot(x)-\csc(x)\sin(2x))dx\]
OpenStudy (anonymous):
\[\int\limits \csc(x)\cot(x) dx - \int\limits \csc(x)\sin(2x) dx\]
OpenStudy (anonymous):
now here for sin(2x) i will use the trig identity you provided in the hint which is sin(2x) =2sin(x)cos(x)
OpenStudy (anonymous):
and we will use the definition of csc(x)
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OpenStudy (anonymous):
this yields to
OpenStudy (anonymous):
\[\int\limits\limits \csc(x)\cot(x) dx - \int\limits\limits \ \frac{ 1 }{ \sin(x) }2\cos(x)\sin(x) dx\]
OpenStudy (jamesj):
You see? The questioner has gone. Are you there, @bmelyk?
OpenStudy (anonymous):
look at the 2nd integral
OpenStudy (anonymous):
\[\int\limits\limits\limits \csc(x)\cot(x) dx - 2\int\limits\limits\limits \ \cos(x) dx\]
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OpenStudy (anonymous):
\[\int\limits\limits\limits\limits \csc(x)\cot(x) dx= - \csc(x) + C_1\]
OpenStudy (anonymous):
\[- 2\int\limits\limits\limits\limits \ \cos(x) dx=-2\sin(x) +C_2\]
OpenStudy (anonymous):
final answer is:
OpenStudy (anonymous):
\[=-(\csc(x) + 2\sin(x)) + C\]
OpenStudy (anonymous):
i hope this helps sorry my net is frustrating today