- #1
escryan
- 13
- 0
Homework Statement
Given y=xtanx, find y'' (second derivative)
Homework Equations
Uh... I'm not even sure if I'm using the right one...
d/dx(tanx) = sec^2x
The Attempt at a Solution
y=xtanx
y'= (x)(sec^2(x)) + (tanx)(1)
y'= xsec^2(x) + tanx
y'' = [(x)(2sec^3(x)) + sec^2(x)(1)] + sec^2x
y'' = 2xsec^3(x) + sec^2(x) + sec^2(x)
...
The key answer says it is supposed to be (2cosx + 2xsinx)/(cos^3(x))