given
A= (10 sqrt2) (cos pi/4), pi/4 is a radian, solve for A

I know the answer is A=10 but I cannot figure out how do to this.
I think pi/4 is cos45 but not sure. For the example, they just told me that (cos pi/4) = sqrt2/2, but I cannot figure out how to either use a table or calculator to
find this.

Question

given 
A= (10 sqrt2) (cos pi/4), pi/4 is a radian, solve for A

I know the answer is A=10 but I cannot figure out how do to this. 
I think pi/4 is cos45 but not sure. For the example, they just told me that (cos pi/4) = sqrt2/2, but I cannot figure out how to either use a table or calculator to 
find this.

anonymous · Answer

This comes from... http://www.khanacademy.org/math/trigonometry/v/using-trig-functions

anonymous · Answer

Can you tell me what the value of cosine is at pi/4? 
Look at the unit circle (memorize it)

anonymous · Answer

value of cosine at pi/4= 0.70711? I do not know what to do after that.

anonymous · Answer

Well, you are given that the value of cos(pi/4) = sqrt(2)/2. This is what we call an EXACT value. 0.70711 is an APPROXIMATE value. I would definitely learn the unit circle. But then what you get is this:
|dw:1344030130629:dw|
right?