Given that d/dx(cosx)=-sinx show that d/dx(secx)=secx(tanx)

let y=sec(x) = 1/(cos(X)) = cos(x)^-1

Thus dy/dx = -1(cos(x))^-2(-sinx) = sin(x)/(cos(x))²

= 1/cos(x)  x  sin(x)/cos(x)

=sec(x)tan(x)