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avatar+237 

Given sin(−θ)=−1/4 and tanθ =√15 / 15

What is the value of cosθ ?

 

A) −√15 / 4
 

B) −√15 / 60

 

C) √15 / 4

 

D) √15 / 60

jjennylove  Nov 17, 2018
 #1
avatar+92785 
+2

Note....   sin (-θ)  =  -sin(θ)

 

And  tanθ =√15 / 15  =   1 / √15 

 

So

-sin (θ)  = -1/4  ⇒   sin (θ) = 1/4

 

And

 

tan (θ)  =  sin (θ)  / cos(θ)       rearrange as

 

cos (θ)  =  sin (θ)  / tan (θ)   =   (1/4)  / (1/ √15)   =  (1/4) * (√15 / 1)  = √15 / 4  ⇒  C

 

 

cool cool cool

CPhill  Nov 17, 2018
 #2
avatar+237 
+1

Much more easier then I anticipated. I was thinking it was that one but I found it more diffuclt but seeing the steps you used which are more simple . Thank you smiley

jjennylove  Nov 17, 2018
edited by jjennylove  Nov 17, 2018
edited by jjennylove  Nov 17, 2018
 #3
avatar+92785 
+1

Thanks....sometimes it helps to  "un-rationalize" the denominator on those square root ratios   ....[if that's even a word.....LOL!!!!  ]

 

 

 

cool cool cool

CPhill  Nov 17, 2018
 #4
avatar+2294 
+2

I guess you could consider it to be a rationalization of the numerator.

TheXSquaredFactor  Nov 17, 2018
 #5
avatar+92785 
+1

HAHAHA!!!!!.....that sounds better, X2......!!!!!

 

 

cool cool cool

CPhill  Nov 17, 2018

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