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# Given sin(−θ)=−1/4 and tanθ =√15 / 15

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+1898

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

Nov 17, 2018

#1
+111326
+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

Nov 17, 2018
#2
+1898
+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

jjennylove  Nov 17, 2018
edited by jjennylove  Nov 17, 2018
edited by jjennylove  Nov 17, 2018
#3
+111326
+1

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

CPhill  Nov 17, 2018
#4
+2419
+2

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

TheXSquaredFactor  Nov 17, 2018
#5
+111326
+1

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

CPhill  Nov 17, 2018