How to solve cos( 11 pi/4

Question

jdoe0001 · Answer

you're asked for the angle?

jdoe0001 · Answer

I mean, there's nothing to solve per se

anonymous · Answer

It's asking for the exact value of the trigonometric function

jdoe0001 · Answer

https://www.google.com/search?client=opera&rls=en&q=cos(+11+pi/4)&sourceid=opera&ie=utf-8&oe=utf-8&channel=suggest

anonymous · Answer

convert 11pi/4 rads into degrees. 11*180/4 = 495 deg

495 deg = 135 deg

135 deg is in Quadrant II on the unit circle

135 deg will create a triangle of 45 deg when going down to the x-axis

Now you have a 45-45-90 triangle whose sides must be 

sqrt(2)/2 for the adj.
sqrt(2)/2 for the opp.
1 for the hypotenuse.

Cosine = adj/hyp

Cos = sqrt(2)/2

But since it's in the second quadrant its adj. side is negative so

cos(11pi/4) = -sqrt(2)/2

anonymous · Answer

That's exactly what I needed, thank you.  I didn't realize it created a 45-45-90- triangle. Thank you.