The TAN function in Excel is used to calculate the tangent of a given angle. It takes a single argument, the angle in radians, and returns the tangent of that angle. The function is part of the Math & Trig group of functions.

The function can be used in a variety of calculations, such as finding the angle of a triangle or the length of a side. It can also be used to calculate angles in trigonometry or in graphics applications.

To use the function in Excel, enter the angle in radians in a cell and then use the formula =Tan(angle). The result will be the tangent of the angle.

For example, if you want to find the tangent of an angle of 30 degrees, the formula would be =Tan(30*PI()/180). The result is 0.57735026919.

The function can also convert an angle in degrees to radians by multiplying the angle in degrees by PI()/180. For example, if you want to convert 45 degrees to radians, the formula would be =Tan(45*PI()/180), which will return the result 0.78539816339.