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ketz
 one year ago
Can anybody explain tom me why when solving cos x >0.69? ...The answer is x<46.4 degrees?? why the inequality sign changes?
ketz
 one year ago
Can anybody explain tom me why when solving cos x >0.69? ...The answer is x<46.4 degrees?? why the inequality sign changes?

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kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1Do you have the graph of cosine?

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1Actually, the value of cosine goes down when x goes up

ketz
 one year ago
Best ResponseYou've already chosen the best response.0So inequality signs are not only supposed to be flipped when divide by negative number or multiply by negative number??

ketz
 one year ago
Best ResponseYou've already chosen the best response.0I thought it was only for the condition i stated above that inequality changes sign!!

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1Well, there are many conditions in which the inequality changes sign

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1You aren't multiplying something to the inequality here

ketz
 one year ago
Best ResponseYou've already chosen the best response.0Can you enumerate all of them please...

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1Well, in general, when you apply decreasing functions to both sides of an inequality, it changes signs.

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1Decreasing functions are those whose graphs go down.

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1dw:1434221346342:dw

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1This is a part of the cosine graph

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1You can see that if \(\cos x > 0.69\), \(x < \ \)something.

ketz
 one year ago
Best ResponseYou've already chosen the best response.0Thxs...Is there any other conditions to change the inequality sign? Can you provide a link...

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1Okay, those functions are called "decreasing functions". I'm searching for a list.

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1I can't really find a list available...

ketz
 one year ago
Best ResponseYou've already chosen the best response.0but how do you know all of them?

kc_kennylau
 one year ago
Best ResponseYou've already chosen the best response.1I can't know all of them, but in the case of cosine, I know the shape of the cosine graph.
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