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December 23rd, 2017, 04:28 AM  #1 
Newbie Joined: May 2017 From: uk Posts: 9 Thanks: 0  stationary points of a trig function
Hi, am I doing this right? Find the coordinates when the gradient of this function is equal to zero t = cos(θ) f '(t) = sin(θ) $\ \ \ \ \ \ \ \ $ = sin(θ) = 0 $\ \ \ \ $ θ = 0/sin $\ \ \ \ $ θ = 0 Plug 0 in to original equation t = cos(0) t = 1 Coordinates = 0,1 where gradient is zero. Last edited by skipjack; December 23rd, 2017 at 08:27 AM. 
December 23rd, 2017, 05:13 AM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,765 Thanks: 1014 Math Focus: Elementary mathematics and beyond 
$\sin\theta$ is periodic.

December 23rd, 2017, 08:30 AM  #3 
Global Moderator Joined: Dec 2006 Posts: 18,704 Thanks: 1530 
Having obtained sin(θ) = 0, one cannot divide by "sin". Instead, solve sin(θ) = 0 by using knowledge of the sin function. 

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function, points, stationary, trig 
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