+128623 (tan x - sec x)^2 = (1 - sin x)/(1 + sin x)
tan^2x - 2tanxsecx + sec^2x
tan^2x - 2tanxsecx + [ tan^2x + 1 ]
2tan^2x -2tanxsecx + 1
2sin^2x/cos^2x - 2 [sinx]/cos^2x + [cos^2x / cos^2x ]
[ 2sin^2x - 2sinx + cos^2x] / cos^2x
[ 2sin^2x - 2sinx + (1 - sin^2x ) ] / cos^2x
[sin^2x - 2 sinx + 1] / cos^2x factor the numerator
[sinx -1] [sinx - 1] / [ 1 - sin^2x]
[sinx -1] [sinx - 1 ] / ( [ 1 + sinx ] [ 1 - sinx] ) factor -1 out of the numerator
- [ 1 - sinx] [ sinx - 1] / ([1 + sinx] [ 1 - sinx ] )
- [sinx -1] / [ 1 + sinx]
[1 - sin x ] / [ 1 + sin x ]
