How do you find exactly #sin 78.75^o#, in a closed form?

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Answer 1 · 2016-11-09T02:27:00

#sqrt(((1+sqrt((1+1/sqrt 2)/2))/2)#=0.98078528, nearly.

#sin (78.75^o)#

#=cos(90^o-78.75^o)#

#=cos (11.25^o)#

#=sqrt(((1+cos(22.5^o))/2)#

#=sqrt(((1+sqrt((1+cos(45^o)}/2))/2)#

Note for information:: A completed joint paper by me and two

others in USA, presenting an innovative generalizaion of this

method, is on the rounds, expecting publication in a repute journal.