Tuesday, May 5, 2009

`y = tanh^-1(sqrt(x))` Find the derivative of the function

Derivative of a function f with respect to x is denoted as `f'(x)` or ` y'` .


To solve for derivative of y or `(y')` for the given problem: `y = tanh^(-1)(sqrt(x))` , we follow the basic derivative formula for inverse hyperbolic function:


`d/(dx)(tanh^(-1)(u))= ((du)/(dx))/(1-u^2) ` where `|u|lt1` .


Let: `u =sqrt(x)`


Apply the Law of Exponent: `sqrt(x) = x^(1/2)`


Solve for the derivative of u using the Power Rule for derivative: `d/(dx)x^n=n*x^(n+1) * d(x)`


Then,


`du=1/2x^(1/2-1)*1dx`


`du=1/2x^(-1/2) dx`


Apply the Law of Exponent:


`x^(-n)= 1/x^n. `


`du=1/(2x^(1/2)) dx `


Rearrange into:


`(du)/(dx)=1/(2x^(1/2))`


`(du)/(dx)=1/(2sqrt(x)) `      


Apply the derivative formula, we get:


`d/(dx)(tanh^(-1)(sqrt(x)))= ((1/(2sqrt(x))))/((1-(sqrt(x))^2))`


                               `=((1/(2sqrt(x))))/((1-x))`


                               `=(1/(2sqrt(x)))*1/((1-x))`


                               `=1/(2sqrt(x)(1-x))`


Final answer:


`d/(dx)(tanh^(-1)(sqrt(x)))=1/(2sqrt(x)(1-x))`

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