Posted by CJ on Thursday, January 13, 2011 at 4:33pm.
cos^-1 (√5/6)
is an angle Ø so that sinØ = √5/6
sketch a right-angled triangle with hypotenuse 6, and opposite side √5
by Pythagoras the adjacent side is √31
then cosØ = √31/6
so sin(cosˉ¹√5/6) = √31/6