How do we approximate f^(-1)(x)f1(x)?

Iff(x)=x+sin(xpi)f(x)=x+sin(xπ), how could we go about trying to find its inverse over an interval on which ff is invertible?

1 Answer
Nov 17, 2017

We have:

f(x)=x+sin(pix) f(x)=x+sin(πx)

If we let:

y = x+sin(pix) y=x+sin(πx) ..... [A]

Then, the inverse, f^(-1)(x)f1(x) would normally be obtained by re-arranging equation [A] into the form:

x = g(y) x=g(y)

Making gg the inverse.

However we cannot perform such a re-arrangement using the standard elementary functions that we are familiar with.

This is where the "approximation" component comes in because given any particular constant value of xx, (let us call this value alphaα, say) we would find the inverse f^(-1)(alpha)f1(α) by solving numerically the equation:

x+sin(pix) =alpha x+sin(πx)=α