Maths question calculus

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xcos^2(3x) =1 solve for x

Sep 9th, 2015

Thank you for the opportunity to help you with your question!

cos2(x) = 1/2 + 1/2 cos(2x)
xcos^2(3x) = x[1/2 + 1/2 cos(6x)]=1
1/2 + 1/2 cos(6x)=1/x


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Sep 9th, 2015

thanks a lot

How to solve for x ? What values of x will satisfy this equation ? 

Sep 9th, 2015

1/2cos(6x)=1/x-1/2

cos(6x) =2/x - 1

cos(6x) = cos2(3x) – sin2(3x) = 1 – 2sin2(3x) = 2cos2(3x) – 1

-[cos2(3x) - sin2(3x)] =2/x - 1

1= 2/x - 1

x=1

Sep 9th, 2015

Thanks The choice of answers is 1.01 and 1.18 the question is more like <= x <= pie/2 at which values of x do the graphs of f(x)=2 tan(3x) and g(x) = 3x^2 have parallel tangent lines 

Sep 9th, 2015

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