(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Determine all x in [-pi/2, pi/2] at which the graph has horizontal tangents.

2. Relevant equations

1.) f'(x)= 9cos(x)-2sin(x)

2.) f'(x)= -5csc(x) (5cot(x)-csc(x))

3. The attempt at a solution

1.) 9cos(x)=2sin(x)

9/2=sin(x)/cos(x)

9/2=tan(x)

and then I'm not sure what to do with 9/2?

2.) 5cot(x)=csc(x)

5= csc(x)/cot(x)

5=1/cos(x)

cos(x)=1/5

same problem here... what do I do with 1/5?

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# Finding horizontal tangents on an interval

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