Question

Question #af447

Answer 1

`cos(pi/8)+cos((3pi)/8)+cos(5pi/8)+cos(7pi/8)`

`=cos(pi/8)+cos((3pi)/8)+cos(pi-(3pi)/8)+cos(pi-pi/8)`

`=cos(pi/8)+cos((3pi)/8)-cos((3pi)/8)-cos(pi/8)`

`=0`