For the simple rightangled triangle below, the tangent of the angle θ, is the ratio of the opposite side, o, to the adjacent side, a.
I.e. for the triangle above,
The Excel TAN function calculates the tangent of a given angle.
The syntax of the function is:
Where the number argument is the angle, in radians, that you want to calculate the tangent of.
Converting from Radians to Degrees
If your angle is in degrees, you will need to convert it into radians before supplying it to the Tan function.
This can be done by using the Excel Radians function:
The following spreadsheet shows the Excel Tan Function, used to calculate the tangent of four different angles.
Formulas:

Results:

Note that in the above examples:
For further information and examples of the Excel Tan function, see the Microsoft Office website.