[latex]T:\\ frac{sin alpha }{cos alpha -1} -frac{sin alpha }{cos alpha +1} = frac{-2}{sin alpha } \\Dw:\\L= frac{sin alpha }{cos alpha -1} -frac{sin alpha }{cos alpha +1}= frac{sin alpha(cos alpha +1) }{(cos alpha -1)(cos alpha +1)}- frac{sin alpha(cos alpha -1) }{(cos alpha -1)(cos alpha +1)}=\\ frac{sin alpha(cos alpha +1) -sin alpha(cos alpha -1) }{(cos alpha -1)(cos alpha +1)}=[/latex] [latex]frac{sin alpha cos alpha +sin alpha-sin alpha cos alpha -sin alpha }{cos^2 alpha -1}= frac{-2sin alpha }{sin^2 alpha } = frac{-2}{sin alpha } =P\\cbdo [/latex]
[latex]\L= dfrac{sin alpha }{cos alpha -1} - dfrac{sin alpha }{cos alpha +1} = dfrac{sin alpha (cos alpha +1)-sin alpha (cos alpha -1)}{(cos alpha -1)(cos alpha +1)} = \ \ \ dfrac{sin alpha cos alpha +sin alpha -sin alpha cos alpha +sin alpha }{cos^2 alpha -1} = dfrac{2sin alpha }{cos^2 alpha -sin^2 alpha -cos^2 alpha } = \ \ \ dfrac{2sin alpha }{-sin^2 alpha } = dfrac{-2}{sin alpha } , alpha eq frac{kpi}{2} \ \ \L=P[/latex]
