Here is the formula I was given by a coworker.
He asked if I could solve for x.

y = tan(x) - (x*PI/180)

I have failed. Can anyone else solve this?
This formula will find the y value if you know what x is, but we want to reverse it so that it will find the x value if we know what y is.

Good luck...

This function has no inverse. Check out the graph: http://po.st/ZVqvwH

Hmmm.. that is interesting. Thanks.

If you restrict the domain to (-pi/2;pi/2), the function becomes a bijection. f(x) = y, then f^-1(a) = b such that atan(b) = b * 180 / pi - a * 180 * pi

Just out of curiosity, what are your measurement units? Your equation looks highly unusual:

x*\pi /180 is the formula to convert from degrees to radians

so I am suspicious that your coworker made a measurement unit error (perhaps not, but then the equation is highly unusual).

Do you actually want to solve this problem (say, by writing a program that gives you an approximate value of y), or was your coworker challenging you just to show off (say, his math mojo)?

Do you have restrictions on how fast your subroutine finding y should run?

Do you have upper bounds on y? [Edit] on a second thought that doesn't sound necessary. You can always say something like: "if y>10^100, we assume that x is approximately equal to \pi/2", and then work within a reasonable range for y.

Do you have requested answer precision for y?