The graph of a sinusoidal function intersects its midline at ( 0 , − 6 ) (0,−6)left parenthesis, 0, comma, minus, 6, right parenthesis and then has a minimum point at ( 2.5 , − 9 ) (2.5,−9)left parenthesis, 2, point, 5, comma, minus, 9, right parenthesis. Write the formula of the function, where � xx is entered in radians. � ( � ) = f(x)=f, left parenthesis, x, right parenthesis, equals