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.

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