lim Cot(2x) Sin(6x) (l'hospital's rule section)
x -> 0
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OpenStudy (dumbcow):
to apply L'hopitals rule you need to put it in fraction form
\[\rightarrow \frac{\cos(2x) \sin(6x)}{\sin(2x)}\]
now differentiate, use product rule for numerator
(fg)' = f'g + fg'
OpenStudy (anonymous):
what he said
OpenStudy (anonymous):
take the derivative of the top.. and the bottom separately
[-2sin(2x)sin(6x) + 6cos(2x)cos(6x)] / -2cos(2x)
OpenStudy (anonymous):
= [-sin(2x)sin(6x) + 3cos(2x)cos(6x)] / -cos(2x)
OpenStudy (anonymous):
= 0 + 3 * 1 / - 1
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OpenStudy (anonymous):
= -3
OpenStudy (anonymous):
actually answer is positive 3
OpenStudy (anonymous):
but i figured it all out now, ty both
OpenStudy (anonymous):
er yeah sorry should have been -6cos(6x)... equating to 3 srry
OpenStudy (anonymous):
no, the deriv of sin is cos... not -cos. problem was in the denom. but moot point.. i got it!!
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OpenStudy (anonymous):
i will give you medal anyway :D
OpenStudy (anonymous):
errrrr sorry late night i meant to say 2cos(2x) :) :) read the wrong thing