Ok, the basic principle here is that tanΘ = sinΘ/cosΘ, so sinΘ = 8/h and cosΘ = 9/h. That said, the value of the sin 2 is the value of the sin 2, which is not dependent on what you introduced the problem with. Are you sure you typed it out exactly as is written in the book? Is it not sin(2Θ)?