cos(x)/(1+sin(x)) =sec(x)-tan(x)
OK, on the right side we have
1/cos(x) - sin(x)/cos(x)
(1 - sin(x)) / cos(x) Multiply numerator and denominator by cos(x)
[(cos(x)* (1- sin(x)] / [cos2(x)]
[(cos(x)* (1- sin(x)]/ (1 - sin2(x))
[(cos(x)* (1- sin(x)]/ [(1 + sin(x)) * (1 - sin(x)]
cos(x)/(1+sin(x)) which equals the left hand side