Hi,

(cosx, sinx) Summary Unit Circle

.

cos(1043π) = cos(π + 1042π) = cos(π) = -1

.....

cos(163π) = cos(π + 162π) = cos(π) = -1

.....

cos(164π) = cos(0 + 164π) = cos(0) = 1 

Answer by lwsshak3(11628)   (Show Source): You can put this solution on YOUR website!
 Why do

cos(1043π)

rotate cc 1042π + π which becoms the reference angle in quadrant I

cos(1043π)=cosπ=-1

..

cos(164π)

rotate cc 164π, which terminates at 0, which becomes the reference angle

cos(164π)=cos 0=1 (contrary to your statement)

..

cos(163π)

rotate cc 162π + π which becoms the reference angle

cos(163π)=cosπ=-1 



Note: even number of π's terminate at 0; whereas, odd number of π's terminate at π 

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