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# Calculus with a natural log watch

1. In a submarine cable the speed of the signal ,v , is related to the radius of the cable's covering. R . by v=(25/R^2) ln(R/5)

Use calculus to calculate the exact values of v and R at this maximum signal speed
2. (Original post by RayRobson)
In a submarine cable the speed of the signal ,v , is related to the radius of the cable's covering. R . by v=(25/R^2) ln(R/5)

Use calculus to calculate the exact values of v and R at this maximum signal speed
Use the product and chain rule to find dV/dr. You should be familiar with the derivative of ln[f(x)] = f '(x)/f(x). Then find the stationary points.

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Updated: November 8, 2015
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