+1995 cos(−θ)=√3/4 , sinθ < 0
What is the value of sinθ ?
A ) √13 / 4
B) √13 / 16
C) − √13 / 4
D) −√13 / 16
I think its C but im not sure I feel like I am way off
+129852 Note cos (-θ) = cos(θ)
So
cos(θ) = √3/4 = x / r
And
sin (θ) = y / r
We need to find "y" ....since r is always positive and the sine < 0....then y must be negative
So
y = -sqrt ( r^2 - x^2) = - sqrt ( 4^2 - (sqrt(3) )^2 ) = - sqrt ( 16 - 3) = -sqrt (13)
So.....
sin (θ) = - √13 / 4 ⇒ C
+1995 While you were composing the answer I used your explanation from the question before and it helped me be more certain on C and now with the explanation above it is clear it is C . 
Thank You
