stuck... again

[Short term memory]

problem: Simplify F(x) = 1 / ( 1+tan^2 x)^.5 - cos x :0<x<pi/2

ok the only thing i can think of to substitute in was (1+tan^2 x)^.5 = sec^2 x ...

so i got the problem down to 1 / (sec^2 x)^.5 + cos and then become stucks

i m thinken i can just say it is 1 / (sec x) + cos... not sure if that will work or not

thanks in advance for any help

[3.14159265358979]

You're on the right track...here's a hint: 1\secx = cosx

[Short term memory]

ya but then cos x - cos x = 0....

(i had actually worked it out using that but i didn't think the answer would be zero... esp since the next problem is the same the only differnce is that it is from pi < x < 3 pi / 2)

i guess i just needed a second untainted opion... thanks