#secx - sinxcotx#
# = 1/cosx - sinx(1/tanx)# #color(red)(Note tanx = sinx/ cos x)#
#=1/cos x - sin x (cos x/sin x)#
#=1/cos x - cos x#
#=1/cos x - cos^2 x / cos x#
#= (1-cos^2 x) / cos x#
#=sin^2 x / cos x# (Trig Identities - #color(red)(cos^2x + sin^2 x =1#)
#=tanxsinx# Note (#color(red)(sinx/cosx=tanx#)