How to Find the Maximum and Minimum Speed of a Particle?

hellboy324
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Homework Statement


The position vector of a particle at time t is given by r(t)= 2sin(2t)i + cos(2t)j + 2tk where t >=0.

Homework Equations


v(t) = 4cos(2t)i - 2sin(2t)j + 2k
speed = | v(t) | =√(16cos^2(2t)+4sin^2(2t)+4) = √(12cos^2(2t)+8)

The Attempt at a Solution


I found the velocity and speed, but I have no idea what to do to find out the maximum and minimum speed for this question, someone can teach me?
 
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How do you usually find the extrema of a function?
 
Things are easier in that the question is asking about scalar speed. What does it mean for the derivative when speed hits a peak/trough?
 
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