sina = √15 /4,cosa = - 1/4
sin(π-a) = sina = √15 /4,sin(a+π/2) = cosa = -1/4,
=> sin(π-a)/((sin(a+π/2)+cosa+1 ) = √15 /4 / ( -1/4 -1/4 + 1) = √15 / 2