Okay, can I tell you what I did and you tell me where I went wrong?
So to solve b) I wanted to find the stationary points, because I can test around the stationary points to find where y is decreasing.
To do this I need to solve secx (2sec^2 x -1)=0 right?
I then solved (sec x) = 0 first and...
I'm sorry can you please explain it again? I don't understand what 0 < x < 2 pi, has anything to do with pi/2 < x < 3pi/2 just because sec x is negative.
Ty!
a) Show that d/dx(secxtanx) = secx (2sec^2 x -1)
b) Hence find the values of x for which the function y = secxtanx is decreasing in the interval 0 < x < 2pi.
THANKYOU!