What is the derivative of arcsin(2x)?

2 Answers
Jun 7, 2015

The derivative of this type of trigonometric function is given by the general rule that follows:

If y=arcsin(u), then y'=(u')/(sqrt(1-u^2))

As in this case our u=2x, then u'=2 and we can proceed :)

(dy)/(dx)=2/sqrt(1-(2x)^2)=1/sqrt(1-4x^2)

Jun 7, 2015

The derivative of arcsin(u) is 1/(1+u^2) (See note)

If u = 2x
by the chain rule
color(white)("XXXX")(d arcsin(2x))/(dx)
color(white)("XXXX")color(white)("XXXX")=(d arcsin(u))/(du) * (du)/(dx)

color(white)("XXXX")color(white)("XXXX")= 1/(1+x^2)*2

color(white)("XXXX")color(white)("XXXX")= 2/(1+x^2)

Note:
color(white)("XXXX")I think (d arcsin(u))/(du) = 1/(1+u^2)
color(white)("XXXX")may only be valid if the argument of arcsin is in radians. (Can anyone verify or deny this?)