So: -sinθ=- 1/3

So: sinθ= 1/3 draw a triangle, so cosθ= 2/3 under plus or minus 2.

Original formula =-cosθ/-cosθ- 1+

-cosθ/-cosθ+cosθ (Is there a mistake in this piece?

Or I miscalculated.

But it can be solved by inductive formula)

= 2/5 under the root number of 8+6