Question 1035761
{{{(sin(phi)) / (1 + sin(phi)) - (sin(phi)) / (1 - sin(phi))}}}
Combining fractions we get
{{{(sin(phi)*(1 - sin(phi)) - (sin(phi))*(1 + sin(phi))) / (1 - (sin(phi))^2)}}} = 
{{{-2(sin(phi))^2/(cos(phi))^2}}}=
{{{-2(tan(phi))^2}}}