this problem is very easy ....for beginning ......you have to write the sum: S=cos1+cos2+.......+cos179
and now you have to write this sum in reverse way :
like that:
S=cos179+cos178+........................+cos1
S=cos1 +cos2 +.........................+cos179( you have to gather)
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2S=(cos179+cos1)+(cos178+cos2)+................+(cos1+cos179)
and now you can see that:
cos 179+cos1=2x((cos179+1):2) x(cos(179-1):2)=0
cos 178+cos2=0
2S=0 S=0
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