What is the derivative of y=x sec(kx)y=xsec(kx)?

3 Answers
Mar 23, 2018

As below.

Explanation:

Differentiating y w.r.t. x,

dy/dx=x.{d/dxsec(kx)×d/dxkx}+sec(kx)×(d/dx)xdydx=x.{ddxsec(kx)×ddxkx}+sec(kx)×(ddx)x

=x*seckxtankx×k + seckx=xseckxtankx×k+seckx

=seckx(kxtankx+1)=seckx(kxtankx+1)

=>sec(kx) (1 + kx*tankx)sec(kx)(1+kxtankx)

Explanation:

Using product rule,

d(xsec(kx))/dxdxsec(kx)dx = d(x)/dxsec(kx)dxdxsec(kx) + xd(sec(kx))/dxxdsec(kx)dx

d(xsec(kx))/dxdxsec(kx)dx = sec(kx)sec(kx) + x*k*tankx*seckxxktankxseckx

=> sec (kx) ( 1 + kx tan (kx))sec(kx)(1+kxtan(kx))

Mar 23, 2018

(1+kxtan(kx))/cos(kx)1+kxtan(kx)cos(kx)

Explanation:

y=x/cos(kx)y=xcos(kx)

y=u/vy=uv
y'=(v*u'-v'*u)/v^2

u=x
u'=1
v=cos(kx)
v'=-ksin(kx)

y'=(cos(ks)+kxsin(kx))/(cos(kx)^2) =(1+kxtan(kx))/cos(kx)