If cos degree equals to 0.8641

Question

What is Sin degree? 

I have no idea how to find this. 
Please help me. I got help from two people, but I'm not getting the answer and how they got the numbers either.

Someone says:

cos^2+sin^2=1 

sinDegree=sqrt(1-cos^2degree)

Another person says:

I recognize .8641 as an approximation to √3/2 
if cos x = √3/2 
x = 30° 
sin30° = 1/2 or .5 

using your .8641 
sinx = .5033

Answer 1

Look. If cos(x) = 0.8641, you use your cos^-1 button to get x.

cos^-1(.8641) = 30.22°
sin 30.22° = 0.5033

So, since they gave you the answer in two different ways, as well as a sanity check to see why it makes sense, what is your work, which produces something else?

If you really have no idea, and cannot understand the answer when it is presented, you have some serious study to do.

Answer 2

Ok thank you. that makes more sense. I didn't understand the square root thing they did.

Answer 3

Simran, thanks for asking for me