Give:
cos(15) = sin( )
cos( ) = sin(77)
we are to find the missing degrees.
(a) cos(15) = sin( )
cos(15) = sin(90 - 15)
cos(15) = sin(75)
Therefore we have cos (15) = (75˚)
(b) cos( ) = sin(77)
cos(90 - 77) = sin(77)
cos(13) = sin(77)
Therefore, we have cos(13˚) = (sin 77)