Confused :S

[EnigmaTuring]

Why does (2/Pi.K).(Sin.K(Pi/2)-SinK(Pi/2)) = the series ((-1)^(K+1/2))/Pi.K ???

I understand that Cos (K.Pi) = (-1)^K but when does Sin equal (-1)^K or (-1)^(K+1/2)??

Thanks.

 

[Ishuda]

Why does (2/Pi.K).(Sin.K(Pi/2)-SinK(Pi/2)) = the series ((-1)^(K+1/2))/Pi.K ???

I understand that Cos (K.Pi) = (-1)^K but when does Sin equal (-1)^K or (-1)^(K+1/2)??

Thanks.

I'm not sure about your first equation but possibly some trig identities would be of help.