Question 1123878
{{{ sqrt(1-csc^2(y))*(cos^2(y)-1))}}}
={{{sqrt((1-1/sin^2(y))*(cos^2(y)-1))}}}
={{{sqrt((sin^2(y)-1)*(-sin^2(y))/sin^2(y))}}}
={{{sqrt(1-sin^2(y))}}}
={{{sqrt(cos^2(y))}}}
={{{Abs(cos(y))}}}