How do you evaluate #cos ((15pi)/4)#?
1 Answer
Jun 25, 2016
Explanation:
We can look at this by considering the angle on the unit circle, where
graph{(y^2+x^2-1)((y+0.7071)^2+(x-0.7071)^2-.001)((y)^2+(x-0.7071)^2-.001)=0 [-2.434, 2.433, -1.215, 1.217]}
From this it is easy to see that the same value repeats itself for each full revolution on the circle, i.e.
In our case we have an angle which is almost 4 full rotations:
Therefore