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Trig question help. Please explain. I think the answer is supposed to be -1 but how do you know that it cannot be the other choices?

Guest Feb 14, 2018
edited by Guest  Feb 14, 2018
 #1
avatar+89775 
+1

Look at the secant graph here :

 

https://www.desmos.com/calculator/g2ulbffk6j

 

Note  that  the range  is   ( - inf, -1 ] U [ 1, inf )

 

So.....the secant's  range  always has an absolute value   ≥  1

 

Only the first answer  meets that criteria....so....you are correct  !!

 

 

cool cool cool

CPhill  Feb 15, 2018
 #2
avatar+1793 
+1

We know that sec(x) is equal to cos(x) because it is the reciprocal of cosine.

 

So, choice d cannot be correct because cos(x) cannot be 0, because it would result in an undefined answer. 

 

We we know that cosine is adjacent/ hypotenuse. Of course, the reciprocal would be hypotenuse/adjacent. 

 

If if you look at choice b, c, and e, the numerators (hypotenuse) are all smaller than the denominator (adjacent side). This is not possible because the hypotenuse in a triangle cannot be less than one side. 

 

this is why choice A must be correct

Mellie  Feb 15, 2018

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